In order to find what the variable equals, you need to put it alone on one side of the equation. So to get rid of the 5, you have to do the opposite of division, which is multiplication. You multiply 5 and 3 to get 15. This will look like:
15 = J
Usually, there is something left to do on the number side, but in this case, there is nothing and you found your answer!
Substitute 4x in for y in the second equation and you get 5x=5. Divide out 5 and you get x=1. Then, you can plug 1 in for x into either equation and solve for y.
