You can start by multiplying the first equation by twelve, by doing this you get whole numbers. This yields: 4x + 3y =12 2x - 3y = -30 As you can see, you have two terms that only differ in sign. By adding both equations together you get this: 6x=-18 or x=-3 The reason why you can add these equations together is illustrated in the next example: 4=x 5=y 4+5=x+y Simple no? Now that you now x you can substitute the value in one of the equations and you get the y value: 4*-3 + 3y =12 -12 + 3y =12 3y= 24 y=8
