Question

Guess the number. The number has two digits. The sum of the digits is eight. If the digits are reversed, the result is 18 less than the original number. What is the original number?

Answer 1

53 would be the answer

Answer 2

Imagine the digits are A and B (for the mystery number AB)

A + B = 8 [1st equation]

AB - BA = 18
A*10 + B - 10*B - A = 18
9A - 9B = 18 / divide everything by 9
A - B = 2 [2nd equation]

If you add the two equations you get

2A = 10
A = 5

So B = 8 - 5 = 3

So the number is 53