closure task

1-js/06-advanced-functions/03-closure/6-closure-sum/solution.md

@@ -0,0 +1,17 @@
+For the second parentheses to work, the first ones must return a function.
+
+Like this:
+
+```js run
+function sum(a) {
+
+  return function(b) {
+    return a + b; // takes "a" from the outer lexical environment
+  };
+
+}
+
+alert( sum(1)(2) ); // 3
+alert( sum(5)(-1) ); // 4
+```
+