Question

the dum of the digits of a 2-digits is 15 the number obtained by reversing the digits is 9 less than the original number find the number

Answer 1

Let the number be ab = 10a + b

a + b = 15

The new number is ba = 10b + a

ba = ab - 9

10b + a = 10a + b - 9

9a - 9b = 9

a - b = 1

2a = 16

a = 8

b = 7

Number is 87