So A plus B must be equal to 150, is equal to 150. And now we have a system of two equations and two unknowns, and so we know how to solve those. We could do it by substitution, or we could subtract the second equation from the first. So let's do that. Let's subtract the left-hand side of this equation from that. So, or essentially, we could add these two, so we can multiply this one times a negative one, and then add these two equations. The A's are going to cancel out, and we are going to be left with six B minus B is five B, is equal to 375, is equal to 375.