+128475 Look at the following graph : https://www.desmos.com/calculator/rfebje54mw
The first two constraints just tell us that we are in the first quadrant...we can ignore them
The x/y coordinates that maximize the objective function occur at the cornrer point (12,5)
So...the max value is
C = 7(12) + 9(5) = 84 + 45 = 129
