Question

find the digit sum of the given numbers? 1.2364 2. 8091​

Answer 1

Let the digit at the tens place be x and the digit at the unit place be y. 

x+y=12  ...(1)

Required Number = (10x+y).

Number obtained on reversing the digits = (10y+x).

According to the condition, we get

(10y+x)−(10x+y)=18

→ 9y−9x=18

→   y−x=2     (2)

Adding (1) and (2), we get

2y=14 →y=7

 → x= 12 - 7 = 5

Hence, the required number is 57.