Question

http://prntscr.com/3ggosz

Answer 1

Here...
$67.5 --> the cost for 9 pizzas
$ ? ---> the cost for 1 pizza

This is what they mean by the unit cost. They want to know how much 1 pizza will cost. (unit means "one").

So, all you need to do is divide the cost by 9. But if you're wondering about the units... just keep in the "same" order. Since we're diving the cost by the number of pizzas:
\[\frac{$67.5}{9\text { pizzas}}=\frac{$7.50}{\text{ pizza}}\]