Question

A number consists of two digits whose sum is 9. If 27 is subtracted from the original number, its digits are interchanged.Then the original number is

Answer 1

Let number be x and y

x+y=9------(1)

10x+y-27=10y+x
9x-9y=27
x-y=3-----(2)

Adding both equation

2x=12
x=6

Putting x in equation 1

x+y=9
6+y=9
y=9-6
y=3

Answer 2

let tens digit be x and ones digit be y
x+y=9

eq. 2
10x+y-27=10y+x
9x-9y=27
x-y=3
Adding both eq we get
2x=12
x=6
y=3
number=63