Using VERTICALLY AND CROSSWISE you do not need to the multiplication tables beyond 5 X 5.

8 is 2 below 10 and 7 is 3 below 10.

Think of it like this:

The answer is 56.

The diagram below shows how you get it.

You subtract crosswise 8-3 or 7 - 2 to get 5,

the first figure of the answer.

And you multiply vertically: 2 x 3 to get 6,

the last figure of the answer.