Question

the sum of the digit of a two digit number is 3 if we subtract 9 from the number the digits are interchamge find the original number

Answer 1

Let unit's digit be y
and ten's digit be x
x+y=3
10x+y-9=10y+x
9x-9y=9
x-y=1
x+y=3
x=2 and y =1

Answer 2

Let the digits be x and y .
Fraction = 10 x + y.
Fraction after interchanging digits = 10 y + x.
Now, as per the question
x+ y = 3................eq 1
10x +y -9 = 10y +x
i.e. x-y = 1..,..........eq 2
Equating both the equations ,
you will get
y = 1, x= 2.
Original no. will be 21.