diff --git a/public/sandbox.js b/public/sandbox.js
index 6a0850d..4295eb0 100644
--- a/public/sandbox.js
+++ b/public/sandbox.js
@@ -6,14 +6,14 @@
 // greet = () => {
 //   console.log('hello, again');
 // }
-var add = function (a, b, c /*?*/) {
-    if (c === void 0) { c /*?*/ = 10; }
+var add = function (a, b, c) {
+    if (c === void 0) { c = 50; }
     console.log(a + b);
     console.log(c);
 };
-add(5, 10, 'ninja');
+add(5, 10, "난 세 번째 인자");
 var minus = function (a, b) {
     return a + b;
 };
 var result = minus(10, 7);
-console.log(result);
+//console.log(result);
diff --git a/src/sandbox.ts b/src/sandbox.ts
index 534d3b8..784aeae 100644
--- a/src/sandbox.ts
+++ b/src/sandbox.ts
@@ -8,16 +8,15 @@
 //   console.log('hello, again');
 // }
 
-const add = (a: number, b: number, c/*?*/: number | string = 10): void => {
+const add = (a: number, b: number, c: number | string = 50): void => {
   console.log(a + b);
   console.log(c);
-}
-
-add(5, 10, 'ninja');
+};
+add(5, 10, "난 세 번째 인자");
 
 const minus = (a: number, b: number): number => {
   return a + b;
-}
+};
 
-let result = minus(10,7);
-console.log(result);
\ No newline at end of file
+let result = minus(10, 7);
+//console.log(result);