Find the mistake: two-step equations (Full video)

Khan Academy

Supporting grades: 7

Description: When doing algebra, we sometimes make mistakes! It's important to be able to check our own work (and other people's work) for correctness. What I wanna do in this video is get some practice building an important skill, being able to look at some algebra that has happened and see whether it is correct. So I have an equation, nine times, and then in parentheses, two x plus 1/3 is equal to 39. All right, so let's just work through this problem and see if all of these steps are reasonable.

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