Costello is wrong. When you multiply 7 by 4 it is 28, not 7 by 14. Costello is wrong because when dividing you can't hold a number. Also when he added 14 he counted the one's place correct but not the ten's place correct. Another set of numbers you could use it 8x15=48. You could find this out very easily.

The problem would be set up like this: XY+X=Z

X= the multiplier

Y= the ones digit

X and Y have to be one of the digits 1-9.

For Example:

X=8

Y=5

8x5+8=48

8x15=48