In a triangle the measure of the first angle is six times a number the measure of the second angle is nine less than the first angle measure of the third angle is three times the number more than the measure of the first angle remind the measure of each angle in degrees

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?