@persalteas: If you press Enter, it is executing again from the homescreen, not relooping. Your code is looking for the [Clear] key.
[clear]=15
[enter]=9

If you want, try to put a Pause 20 in there before the Repeat loop and see what happens

@Yeong: I think it doesn't work because I programmed If, Repeat, and While to not affect Ans

Hehe 'Tis okay, you are using Return properly, which is great (Return is really fast, by the way, especially compared to using labels).