HW<9 fixed> done

HW 9/index.html

@@ -14,7 +14,7 @@
                 let t0 = performance.now();
                 return function tn() {
                     let t1 = performance.now();
-                    return t1 - t0 + ` milliseconds`;
+                    return t1 - t0;
                 };
             }