Multiply the first equation by -15, then add it to the second equation to eliminate y.
I'm usually pretty decent doing these problems, but one is stumping me for some reason. I'm drawing a blank on the following turning the fraction into a simple line formula to solve with. It goes like this.
x over 3 plus y over 3 equals 0 so x/3 + y/3 = 0 is the first one and the second is 10x + 5y = -1