Determine which equations correspond to the graphs given below

Julius sold five times as many computers as sam sold last year. in total, they sold 78 computers. how many computers did julius sell?

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?

Anyone know these questions? i need ,.