Let's write the first inequality, the number of people:
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:
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.
After all of this, we can assure that the expressions 5<=n<=8, c=2n, L=c, 10<=L<=16
are completely true.