Here is one of the questions I had trouble with. The mistake I made is that I tried subtracting the equations (x+3y=10 – 5x-3y=14) rather that adding them (x+3y=10 + 5x-3y=14). This did not create a zero pair when subtracted so I had nowhere to go in the equation

When I tried adding the equation, a zero pair was made with 3y and -3y, so I was able to isolate x, then plug x into one of the equations to find y.