in a positive number of two digits,the sum of the digits is 15.if the digits are interchanged the number is increased by 9.find the number.

Answer 1

let the unit digit be x
then the tens digit is 15 - x , (their sum is 15)

original number = 10(15-x) + x
= 150 - 9x

the number reversed = 10x + 15-x
= 9x + 15

What does our question tell us about the relationship between these two expressions?

form your equation and solve for x
sub back into my definitions