Solving proportions 10/8=n/10

The heaviest 16% of all men in weight weigh more than how many pounds ?

Solving algebraic equations 2m+3=11

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?