Two time a number added to another number is 25. Three times the first number minus the other number is 20

Equation 1:

2x + y = 25

-Subtract 'y' to both sides (quick note: pretend 'y' is '1')

2x + 1 - 1 = 25 - 1

2x = 24

-Divide '2' to both sides

2x/2 = 24/2

x = 9

Equation 2: 3y - x = 20

-Add 'y' (or 1) to both sides

3y - 1 + 1 = 20 + 1

3y = 21

-Divide '3' to both sides

3y/3 = 21/3

y = 7