Question 1041607
x+y = 12
x-y = 1/3


Multiply out the two equations (left sides group together, right sides group together)


(x+y)*(x-y) = 12*(1/3)
(x+y)*(x-y) = 4
x^2 - y^2 = 4 ... difference of squares rule



The final answer is 4.