Question

Please explain it in detail

Answer 1

x+y=12
x-y=36
x=36-y
x+y=12 (x=36-y)
36-y+y=12
36=12
12-36=0
24

Answer 2

It means that suppose a two digit number is 34 and the sum of 3+4is 12 . To solve this question you have to do this : Let the number in unit digit be x and the digit in tens place be y then your original number is 10y + x and the sum of x+y =12 . Then by interchanging the digits we get 10x + y