Box of cereal

Ari and Bill share a 20-ounce box of cereal. By the end of the week, Ari had eaten 3/8 of the box, and Bill had eaten 1/4 of the box of cereal. How many ounces are left in the box?

Correct answer:

x =  7.5 oz

Step-by-step explanation:

$$\begin{gathered} m=20\text{oz} \\ f=1-\frac{3}{8}-\frac{1}{4}=\frac{3}{8}=0.375 \\ x=m\cdot f=20\cdot \frac{3}{8}=\frac{20\cdot 3}{8}=\frac{60}{8}=\frac{15}{2}\text{oz}=7.5\text{oz} \end{gathered}$$

Try another example