For me, it is easier to take the 3/5 and put it in decimal form which is .6 and add the 5 to it, making 5.6, and then in a calculator put in 5.6 divided by 12 and you should get a big decimal that's pretty big but if you have a graphing calculator and convert that to a fraction and you should get 7/15, This is a pretty lazy way of me doing it but that's how I did it.
It will be negative 2,cause your equation is already in general form but we can't have a negative on a, so we should changed it on their opposite sign, so 2 will be negative