A) 70 pools in total
B) 5:2
25x-25y that is the answer. You multiply the outside variable with the first variable inside the parenthesis. Next, you do the same thing to the other side and that is your answer. (unless you have to do more work)
check the picture below.
so as you can see, the box is simply 6 rectangles stacked up to each other at the edges.
so we can simply get the area of each rectangle and sum them up and that's the area of the rectangular prism.

C) 2w. If it grows 2cm. every week then it would be 2 times the number of weeks.