EXPLANATION
Given that we have $2.10 and we would need to buy some rolled oats.
If a pound costs $4, we can compute the ounces that we can buy by applying the unitary considering that 1 pound = 16 ounces
[tex]\text{?ounces}=\frac{1\text{ pound}}{4\text{ dollars}}\cdot2.10\text{ dollars}\cdot\frac{16\text{ ounces}}{1\text{ pound}}[/tex]Multiplying numbers and simplifying:
[tex]\text{?ounces}=\frac{33.6}{4}\text{ounces}=8.4\text{ ounces}[/tex]Answer: We could buy 8.4 ounces