diff --git a/BAEKJOON/week07/yejin/Q1110.java b/BAEKJOON/week07/yejin/Q1110.java
new file mode 100644
index 0000000..102f6b4
--- /dev/null
+++ b/BAEKJOON/week07/yejin/Q1110.java
@@ -0,0 +1,32 @@
+import java.util.Scanner;
+
+/**
+ * Q1110
+ * 
+ * #### 제출
+ * 틀렸습니다.
+ * 
+ * -> 파이썬으로 하면 성공인데 어이없음
+ */
+
+public class Q1110 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int n = sc.nextInt();
+        sc.close();
+        int tmpN = n;
+
+        int cnt = 0;
+        while (true) {
+            int a = tmpN / 10;
+            int b = tmpN % 10;
+            int tmp = b * 10 + ((a+b)%10);
+            cnt++;
+            System.out.println(tmp + " " +cnt);
+            if (tmp == n)
+                break;
+            tmpN = tmp;
+        }
+        System.out.println(cnt);
+    }
+}
\ No newline at end of file
diff --git a/BAEKJOON/week07/yejin/Q1312.java b/BAEKJOON/week07/yejin/Q1312.java
new file mode 100644
index 0000000..1099be4
--- /dev/null
+++ b/BAEKJOON/week07/yejin/Q1312.java
@@ -0,0 +1,47 @@
+import java.io.BufferedInputStream;
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.Scanner;
+import java.util.StringTokenizer;
+
+/**
+ * Q1312
+ * 
+ * #### 제출
+ * 실패
+ */
+
+public class Q1312 {
+    // bufferedReader 사용
+
+    // public static void main(String[] args) throws Exception {
+    // BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    // StringTokenizer st = new StringTokenizer(br.readLine());
+    // br.close();
+
+    // int[] arr = new int[3];
+    // int i = 0;
+    // while(st.hasMoreTokens()){
+    // arr[i++] = Integer.parseInt(st.nextToken());
+    // }
+    // double result = (double) arr[0] / arr[1];
+    // int multi = 1;
+    // for (int j = 0; j < arr[2]; j++){
+    // multi *= 10;
+    // }
+    // System.out.println((int)(result * multi )% 10);
+    // }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        Double a = sc.nextDouble();
+        Double b = sc.nextDouble();
+        int n = sc.nextInt();
+
+        String result = Double.toString(a / b);
+        System.out.println(result);
+        int c = result.charAt(n + 1) - '0';
+        System.out.println(c);
+        System.out.println(result.charAt(n + 1) - '0');
+    }
+}
\ No newline at end of file
diff --git a/BAEKJOON/week07/yejin/Q2839.java b/BAEKJOON/week07/yejin/Q2839.java
new file mode 100644
index 0000000..29f4105
--- /dev/null
+++ b/BAEKJOON/week07/yejin/Q2839.java
@@ -0,0 +1,32 @@
+import java.util.Scanner;
+
+/*
+ * 3, 5kg 봉지를 갖고 있음
+ * 
+ * #### 제출
+ * 성공
+ */
+public class Q2839 {
+    public static void main(String[] args) {
+        Scanner scan = new Scanner(System.in);
+        int n = scan.nextInt();
+        int result = 0;
+        scan.close();
+
+        while (true) {
+            if (n % 5 == 0) {
+                result += n / 5;
+                System.out.println(result);
+                break;
+            } else {
+                n -= 3;
+                result++;
+            }
+
+            if(n < 0) {
+                System.out.println(-1);
+                break;
+            }
+        }
+    }
+}
diff --git a/README.md b/README.md
index 5c7ba05..48f8b58 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,7 @@
 |4주차|백준] 덱(10866)<br/>백준] 모음의 수(1264)|https://www.acmicpc.net/problem/10866<br/>https://www.acmicpc.net/problem/1264|
 |5주차|백준] 슈퍼마리오(2851)<br/>백준] 2루수 이름이 뭐야(17350)|https://www.acmicpc.net/problem/2851<br/>https://www.acmicpc.net/problem/17350|
 |6주차|백준] 평균점수(10039)<br/>백준] 덱(10866) [re]|https://www.acmicpc.net/problem/10039<br/>https://www.acmicpc.net/problem/10866|
+|7주차|백준] 소수(1312)<br/>백준] 더하기 사이클(1110) [re]|https://www.acmicpc.net/problem/1312<br/>https://www.acmicpc.net/problem/1110|
 
 </div>
 </details>
@@ -42,6 +43,10 @@
 <br/>
 
 ## 알고리즘 정리
-- ### 자료구조
+- **자료구조**
     - [Deque](https://puddle-horse-c8c.notion.site/Deque-5717b3f2251840b18a92620edadebf62)  -->   [관련 문제 : 백준 10866번](https://www.acmicpc.net/problem/10866)
+- **수학**
     - [에라토스테네스의 체](https://puddle-horse-c8c.notion.site/9e76cf12e0604350a81222705138631d)  -->   [관련 문제 : 백준 1929번](https://www.acmicpc.net/problem/1929)
+- **그리디 알고리즘**
+    - [탐욕 알고리즘](https://puddle-horse-c8c.notion.site/d878145382924792a2cd6216236cf0c6)  -->   [관련 문제 : 백준 2839번](https://www.acmicpc.net/problem/2839)
+