How did you factor our r

The common factor is $r$.

• The first term, $2r$, can be written as $r \times 2$.
• The second term, $\frac{88}{21} r$, can be written as $r \times \frac{88}{21}$.

The distributive property states that $a(b+c) = ab + ac$.
We have $r \times 2 + r \times \frac{88}{21}$.
Comparing this to $ab + ac$, we can see that $a=r$, $b=2$, and $c=\frac{88}{21}$.
So, we can rewrite it as $r \left(2 + \frac{88}{21}\right)$.

Therefore, the equation becomes:

This is how $r$ was factored out.