Let's write the first inequality, the number of people:
![5\leq n\leq8](https://img.qammunity.org/2023/formulas/mathematics/college/y24w3nahtv5ir0qs1wfrysfh85pwxpjd8f.png)
Now, since she plans to prepare 2 cups of water per person, we multiply 5 times 2, and 8 times 2 in the equation above; that will be the number of cups:
![10\leq c\leq16](https://img.qammunity.org/2023/formulas/mathematics/college/wu5fj0rrw0af5wqx046519jups88lcwdes.png)
The next step is to find the number of required scoops. There are two ratios that tell us how many scoops of powder we need.
![\begin{gathered} \frac{4\text{ scoops}}{1\text{ quart}}\rightarrow ratio\text{ 1} \\ \frac{1\text{ quart}}{4\text{ cups}}\rightarrow ratio\text{ 2} \\ 10\text{cups}\cdot\frac{4\text{ scoops}}{1\text{ quart}}\cdot\frac{1\text{ quart}}{4\text{ cups}}\leq L\leq16\text{cups}\cdot\frac{4\text{ scoops}}{1\text{ quart}}\cdot\frac{1\text{ quart}}{4\text{ cups}} \\ 10\leq L\leq16 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/tfiw1t1xz3n8uto9r3fsvzp0qhlk6u4y6n.png)
After all of this, we can assure that the expressions 5<=n<=8, c=2n, L=c, 10<=L<=16
are completely true.