What point in the feasible region maximizes the objective function?

The signs in the obective function tell you that you want to maximize x and minimize y in order to maximize the objective function. The value of x is unconstrained by the last listed constraint, but is restricted by the third one to a maximum of 3. The corresponding y-value is zero, which is allowed by the constraints on y.

The point in the feasible region that maximizes C is (3, 0).

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If you can't reason your way through the problem, graphing can be a big help. (It can help validate your reasoning in any event.)

Here, increasing values of C move the objective function line to the right, so you want the farthest-right point in the feasible region. That's the vertex on the x-axis at lower right: (3, 0).

30 people weigh 160 pounds or more

irrational, cannot