At about the 1:54 mark, the teacher does not multiply the right hand side of the equation by 20 after he multiplies everything on the left hand side by 20. His final answer is also wrong because of this; he should get 15x+8y=20.
Putting an equation in standard form when you have fractions
I show how to solve math problems online during live instruction in class. This is my way of providing free tutoring for the students in my class and for students anywhere in the world. Every video is a short clip that shows exactly how to solve math problems step by step. The problems are done in real time and in front of a regular classroom. These videos are intended to help you learn how to solve math problems, review how to solve a math problems, study for a test, or finish your homework. I post all of my videos on YouTube, but if you are looking for other ways to interact with me and my videos you can follow me on the following pages through My Blog, Twitter, or Facebook.