If the first step in the solution of the equation -9+x=5x-7 is "subtract x", then what should the next step be

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 mean median mode and range?

Which ordered pair is a solution of the equation? 2x+3y=10