Y= -15x+35
You can start by subtracting 3x from both sides to isolate the Y now your equation should look pretty much like this, 1/5y=-3x + 7, then to get rid of the 1/5 you multiply both sides by 5, (1/5y)5=(-3x +7)5, then you have what Y is equal to, Y= -15x + 35. Then to find x, you can just substitute -15x + 35 for Y. Substituted, that should look like, 3x + 1/5(-15x + 35) = 7. From there just solve as usual.