2x+3y = 15

x-3y=3

Solve

By process of elimination. 3y and - 3y get eliminated. Giving you

3x=18

Divide by 3 on each side

Giving you x=6

Plugging it into equation 2 you get

(6) - 3y=3

Taking out the parenthesis you have

6-3y=3

Subtract by 6 on each side giving you

-3y=-3

Divide by - 3 on each side giving you

y=1

So the answer for this equation is x=6 and y=1 or the ordered pair (6,1)