Sum of 2/3 + (-1/3) i cant find the answer

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

For the feasibility region shown below find the maximum value of the function p=3x+2y

The height of a plant, in inches, p years after planting it is given by the polynomial function r(p) = -2p% + 270p. find the height of the plant when p = 90 years.