Please help ASAP this is a exam

Which expression is equivalent to (9x - 3 1/ + 1 3/8)

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?

What is the gcf of 20c^3-5c^4+30c^6