You must graph the two given lines and find their point of intersection. It is (10,5). Shade the areas BELOW each of the 2 lines. One line intersects the y-axis at (0,15) and the other line intersects the x-axis at (12.5,0)
Thus, you have an area defined by the vertices given above.
What to do next? Steal the coordinates of each point and subst. them into the given objective function P = 15x + 20y. For exampel, for (12.5,0), the value of P is 15(12.5) + 20(0) = 187.5.
Find P for each of the remaining 3 vertices.
The largest value of P is the answer to this question.