PLEASE HELP, i will appreciate it

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?

5. write an equation for the line that is parallel to the given line and that passes through the given point. y = –5x + 3; (–6, 3)

Afigure is rotated 180°. if one of the points on the image is g'(4, -8), what were the coordinates of g? (8,4) (8,-4) (4,8) (4,8)