How to solve x + 3y=15

If u want u can assign some numbers to make the soultion correct for example x is - 3 y is 6

x+3y=15

-3+18=15

15=15

You should know how to isolate variables, move the x to the right by subtracting it from both sides. You're left with 3y = 15-x

All you do now is divide by 3 to isolate y, you end up with your final answer, y = 5-x/3