3/4 teaspoon water in each gallon. how much in 5 gallons

We can solve this problem by applying the rule of three:
[tex]\begin{gathered} \frac{3}{4}\text{ ------------ 1 gallon} \\ x\text{ ------------ 5 gallons} \end{gathered}[/tex]then, x is given by
[tex]x=\frac{(\frac{3}{4})(5)}{1}[/tex]which gives
[tex]\begin{gathered} x=(\frac{3}{4})(5) \\ x=\frac{15}{4} \end{gathered}[/tex]that is, Pedro will mix 15/4 teaspoons on 5 gallons.
If we convert this result into a mixed fraction form, we obtain
[tex]\frac{15}{4}=3\frac{3}{4}[/tex]