If and are positive integers, find A*B given that
(AB)_9 + A_9 = B0_9
Express your answer in base 10 (you do not need to include the subscript).
A and B must be integers in the range 0 to 8 (I'll assume here that A and B are both non-zero)
AB_9 is 9A+B
B0_9 is 9*B+0
So 9A+B + A = 9B + 0 or 10A = 8B
The only combination of integers in the range 1 to 8 that satisfy the above equality is A = 4 and B = 5, so A*B = 20 (in base 10).