i totally missed that, Thanks!

...and it won't be one of the other given digits in the expression

1 is already in the expression, nothing to fix.

All of the ?s in an expression will represent the same digit (0-9), and it won't be one of the other given digits in the expression.

Or you should read the description before saying that something's broken.

The following expression has 2 numbers that can fill the "?" 1 and 7 but the test case is rooting for 7?

"?83850-68610=?15240"

783850-68610===715240
true
183850-68610===115240
true

its the only test case failing with me and it should be fixed.