This is a pretty convoluted puzzle. Let's sort things out a bit, okay?
You have a -$75 check, and you need to find a way to make it a +$75 check.
Remember that a withdrawal is an opposite of a deposit.
Here's the solution:
Go to the withdrawal window, and get a slip.
Fill it out, with $75 as the withdrawal.
Now, give this to the teller at the deposit window.