Find two numbers whose sum is 67 and whose difference is 13

You have to solve this system of equations to get the answer. One way you could go about that would be to add the systems together. This will eliminate the y and turn it into a single variable algebra problem. x+y=42 x-y=16 2x = 58 Once you solve that for x, you can plug that result back in to either of the first two equations and solve for y.