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 number be ab. Then
a+b = 15
10b+a = 10a+b + 9
Now solve for a and b, and thus the number

Or, just knowing that ba = ab+9 if b=a+1, you have the number 78

Answer 2

solve for me

Answer 3

superb it was very helpful. thanks