Pizzeria Buonapetito makes a triangular-shaped pizza with base width of 18 inches and height 12 inches as shown. Alice wants only a portion of the pizza, so she makes a vertical cut through the pizza and takes the shaded portion. Lettingxbe the bottom length of Alice's portion andybe the length of the cut as shown, answer the following questions.

Here is a picture of the details above:

Here are the problems:

I'm having a lot of trouble trying to find a formula for her area for the second interval.

How would I approach these problems? Thank you!