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.
In this lesson, we learn how to put an equation in standard form when dealing with fractions. Standard form requires that the coefficient of the x variable cannot be negative, and the common factor between A, B, and C must be one or the least common factor. To eliminate fractions, we find the least common denominator and multiply each term by it. Finally, we cannot have a negative A, so if necessary, we divide by negative one. With these steps, we can easily convert equations into standard form.
Putting an equation in standard form when you have fractions
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