Answer:
[tex]r=\frac{7}{3}[/tex]
Step-by-step explanation:
When given the equation
[tex]\frac{r}{72} =\frac{3}{9}[/tex]
We must multiply each side by 72 in order to isolate r.
[tex]r =\frac{3}{9}*\frac{7}{1} \\\\r=\frac{21}{9} \\\\r=\frac{7}{3}[/tex]