Suppose two individuals (smith and jones) each have 10 hours of labor to devote to producting either ice cream (x) or chicken soup (y). smith's utility function is given by

the sum of all the angles in a triangle are equal to 180

so you can add   the 3 given angles together to equal 180:

5y + 2y + 2y = 180

or since all three angles have the same letter, combine the 3 angles to equal 180:

9y = 180

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