We need to find a common denominator to figure this out. A common demoninator is where the bottom number of both fractions are the same.

You might be thinking, "5 isn't a fraction though!" Well, it turns out that any whole number can be written as a fraction if you put it over 1. So to write 5 as a fraction it would be:

$$\frac{5}{1}$$

So now we have:

$$\frac{13}{3} - \frac{5}{1}$$

There's a problem though, the bottom number isn't the same. To fix this, multiply the top and bottom of the second fraction by 3. You can do this as long as you do it to *both the top and bottom*.

$$\frac{13}{3} - \frac{5\times3}{1\times3}$$

$$\frac{13}{3} - \frac{15}{3}$$

Now that we have the common demoninator, we can subtract the tops of the fractions, and put that over 3.

$$\frac{13-15}{3}$$

$$\frac{-2}{3}$$

which is the same thing as:

$$\mathbf{-\frac{2}{3}}$$

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