Please help me bro I rlly need help

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

What term makes it inconsistent y=2x - 4

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?