Subtract Left to Right

86
- 25 (20 + 5)

To solve 86 - 25, first subtract 20, then subtract 5. After subtracting 20, you have the simpler problem 66 - 5. We illustrate this as follows:

86 - 25   =   66 - 5   =   61
(first subtract 20)    (then subtract 5)

Notice we are removing the leftmost digit of the second number from the first number, then the next digit, and so on.

Let's try another:

73
- 48 (40 + 8)

Subtracting from left to right, you can simplify the problem:

73 - 48   =   33 - 8   =   25
(first subtract 40)    (then subtract 8)

Let's try a more challenging one:

652
- 487 (400 + 80 + 7)
652 - 487   =   252 - 80 - 7   =   172 - 7   =   165
(subtract 400)    (then -80)    (then -7)

This is about as difficult as these types of questions can get.