#### Answer

8a

#### Work Step by Step

The distributive property holds that $a(b+c)=ab+ac$ (for real numbers $a$, $b$, and $c$).
Therefore, $a+7a=(1+7)a=(8)a=8a$.
In this case, we have used the distributive property in reverse to write the given sum as a product. Recall that the coefficient in front of the first term $a$ is 1.