freeCodeCamp/guide/english/mathematics/cross-multiply/index.md

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title: Cross Multiply
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## Cross Multiply

### How to cross Multiply

You start with two fractions that are equal to each other. You take the numerator of the of the first fraction and multiply it to the denominator of the second fraction, and you take the denominator of the of the first fraction and multiply it to the numerator of the second fraction. Then simplify to get the missing x value.

Example:

(4/3) = (x/3)
12 = 3x
x = 4