## Algebra Rule 6

#### How to turn a subtraction of two fractions into one fraction

**Description:**

This is another version of rule 5, but for *subtraction* of two fractions, rather than addition.

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**Howdy!** Here are a few very handy rules of algebra. These basic rules are useful for everything from figuring out your gas mileage to acing your next math test — or even solving equations from the far reaches of theoretical physics. *Happy calculating!*

```\left({a \over b}\right)-\left({c \over d}\right) = {(ad-bc) \over bd}```

This is another version of rule 5, but for *subtraction* of two fractions, rather than addition.

```{3 \over 5}-{1 \over 3} = {(3*3) \over (5*3)} - {(1*5) \over (3*5)} = {(3*3)-(1*5) \over (3*5)} = {9-5 \over 15} = {4 \over 15}```

Algebra rules is a project by two of the folks who run The Autodidacts.

A couple of autodidact math enthusiasts, we were looking for all the rules of basic algebra concisely presented in one place. We couldn’t find such a place, so we made **Algebrarules.com**

These simple rules — applied with a pinch of imagination and a dash of arithmetic — can divide, conquer, and solve just about any practical algebra problem.

If you find errata in the math, bugs in the code of Algebrarules.com, or just want to say *Eh*, please send us a letter or join us on our roost: @rulesofalgebra.