In a 2-digit number, the ten's digit is two times its unit's digit and the number is 12 less than two times the number obtained by interchanging its digits. Find the original number.

84

Assume a 2-digit number = 10x+y

Given x = 2y

Now interchange the digits, number becomes 10y + x

Also now, 2*(10y + x) - 12 = 10x + y

2*( 10y + 2y) - 12 = 10*2y + y

24y - 12 = 21y

3y = 12

y = 4

x = 8

The 2-digit number = 10*8+4

The correct answer is Option (3) → 84