When subtracting dollars, try breaking apart the money into their respective units (20, 10, 5, and 1 dollar bills) and subtracting the like units together and then combining the totals.For example, if you start with $45 and then subtract 2 $10s and 1 $5
Break apart $45s into 4 $10s and 1 $5
Subtract 2 $10s from the 4 $10s and the $5s cancel each other out