-15x - 3y = 3
-15x - 3(5x-1) = 3 [input y]
-15x - 15x - 3 = 3 [distribute 3 over 5x and -1]
-30x - 3 = 3 [combine like terms]
-30x = 6 [add 3 to eliminate the negative]
x = [tex] \frac{6}{-30} [/tex] [divide by -30 to get x alone]
x = [tex] \frac{1}{-5} [/tex] [reduce the fraction]
Hopefully this is helpful enough to get you to your answer