Description: This example demonstrates how we solve an equation expressed such: ax + b = c. It's a little more complicated than previous examples, but you can do it! Created by Sal Khan. Let's say we have 3 times x plus 5 is equal to 17. If it was just 3x is equal to 17, you could divide both sides by 3, and you'd get your answer. So 3 times x literally means.*Teacher Advisor is 100% free.