Question

The sum of the digit of a two digit number is 3 be subtracted 9 from the number the digits are interchanged find the original number

Answer 1

X+Y=3
10x+y-9=10y+x
By solving these equation we get x=2
Y=1
21 IS THE ANSWER

Answer 2

Let the two digit number be XY.
Here X, Y are digits.

According to the question,

X + Y = 3. ..... (1)

The number XY is actually 10X + Y because X is the tens digit and Y is the ones digit.

Subtracting 9 from the number gives the number with reversed digits.

So,

10X + Y - 9 = 10Y + X
9X - 9Y = 9

X - Y = 1. ..... (2)

In the above equation 10Y + X is the reversed number i.e. YX.

Solving (1) and (2), we get

X=2, Y =1

Therefore, the original number is 21.