## Introductory Algebra for College Students (7th Edition)

$-\frac{11}{20}$
To add these two fractions, you must first come up with a common denominator for the both of them. To come up with the common denominator, you ask yourself what is the smallest number that both denominators ($4$ and $5$) can go into evenly. Both $4$ and $5$ can go into $20$ evenly, so you use $20$ as your common denominator. Now you have to convert both fractions so that both have a denominator of $20$. Your first fraction that you have to convert is $-\frac{3}{4}$. You see how many times $4$ goes into $20$, which is $5$ times. You take $5$ and then multiply it with the numerator, $-3$, and you get the fraction: $-\frac{15}{20}$ For the second fraction, you see that $5$ goes into $20$ a total of $4$ times. You multiply $4$ times $1$ (the numerator), and you get the following fraction: $\frac{4}{20}$ Now you take the two converted fractions and plug it back into your original problem, and you have: $-\frac{15}{20} + \frac{4}{20}$ You add the two fractions to get: $-\frac{11}{20}$