So confused on 30 and 31 and need to get them done!

The formula for the circumference of a circle is

C=πd         where d=diameter
lets plug in what we know
C=48π

Since they wanted it expressed in terms of pi, this is where you stop so the answer would be 48π

Answer=48π

31. 
For this one they want you to solve for the surface area. I cant really show this as they want you to draw a picture but i will try and explain it as best i can.

So imagine the prism show was like a cardboard box, and you broke it down so that all of the sides lay flat so it looks like the picture below. Now they want you to find the area of all of those squares. so you should in the end have to of those squares be 5*7=35in² as the area, two be 7*9=63in² as the area and the last two as 5*9=45in² as the area. Good luck!

She should use 12/3 to measure