The sum of the digits of a two digit numberis 12.if the new number formed by reversing the digits is greater than the original number by18,find the original number

Instead of making up a formula, do guess and check.

Two digit number, when added together, makes 12.

9 and 3, so 39 or 93
8 and 4, so 48 or 84,

So on and so forth.

Let a=first digit and b=second digit.

Then, a+b=12.

The original number can be expressed as 10a+b.

In reverse, 10b+a

So, we have 10b+a=10a+b+18

So, you have two equations to solve for a and b

a + b = 12
10b + a = 10a + b +18

a + b = 12

10b + a = 10a + b +18
10b +a - 10a - b = 18
9b - 9a = 18
b - a = 2

a + b = 12
-a + b = 2

eliminating the a's

2b = 10
b = 5

if b = 5
then a = 7

the original number is 57