## Elementary Algebra

We are told: $C = A + B + 40 \\ A = B - 20$ Since it is a triangle, we know: $A+ B+C = 180$ Plugging in $A+B=C-40$ into equation three, we find: $2C - 40 = 180 \\ 2C = 220 \\ C = 110$ We plug this value and equation two into equation one to find: $110 = B -20 + B + 40 \\ 2B = 90 \\ B = 45$ Finally, we obtain: $A = B - 20 = 45 - 20 = 25$