Chapter 14, Class Grade Word Problem

In this video, I show how to use algebra and weighted averages to solve this problem (#21 in homework):
Suppose in a class you have grades of 83 and 77 on the tests, a 93 on the paper, and a homework grade of 71. [Assume: The three tests are worth 70%, the homework 20% and the paper 10%] What grade must you get on the third test to have an 82 average?