To find: Unit price of an item from a grocery store. The price of a...

To find unit price, we divide the given price with the number of units.
In this case, the number of units is 12.9.
So, in fractional form, $\frac{\$2.98}{12.9}$  ounces
Let's divide 2.98 by ${\displaystyle 12.9:2.98÷12.9=0.23}$
Thus, unit price is ${\displaystyle \frac{\mathrm{\$}0.23}{1}}$ ounces
The above unit price can be written as $0.23 ounce which is read as $0.23 per ounce.
Final solution:
The unit price of macaroni and cheese ${\displaystyle =\mathrm{\$}0.23}$ ounces

Answer is given below (on video)