19. th e sum of a two-digit number and the number formed by interchanging the digits is 132. of 12 is added to the number, the new number becomes 5 time the sum of the digits. find the number. the sum of digits. when d

We can write the unknown number as , where both are in the set . (Neither can be 0)

Interchanging the digits makes the number . So



Adding 12 to the number makes it 5 times the sum of the number's digits, which means



Now we can solve the system,



so the original number is 48.