The sum of the digits of a two-digits numbers is 12 and when the digits of the to digit number are interchanged, the new number is 36 more than the original. What is the Original number?

Let the Original number is (X + 10Y)
According to question,
Sum of the digit of the number = 12
X + Y = 12 ----------- (1) When digit interchanged, number become 36 more than original number, so,
10X + Y = 10Y + X + 36
X - Y = 4 ------------------- (2)
On solving equation (1) and (2), we get
X = 8
Y = 4
So, Original number,
= X + 10Y = 8 + 10 × 4 = 48