the slope of the line that passes through the the points (x-4) and (2,8) is -3. what is the value of x?

On a piece of paper graph f(x)=5•(0.4)^x

Solve the equation x/4 - 5= -8 -27 -12 -7 12

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?