keeping in mind that a full pool means a WHOLE or namely 5/5 or 6/6 or for this case 4/4 is a whole, so
[tex]\begin{array}{ccll} gallons&quarters\\ \cline{1-2} 53.5&\frac{4}{4}\\[1em] x&\frac{3}{4} \end{array}\implies \cfrac{53.5}{x}~~ = ~~\cfrac{ ~~ \frac{4}{4}~~ }{\frac{3}{4}}\implies \cfrac{53.5}{x}~~ = ~~\cfrac{1}{ ~~ \frac{3}{4}~~ } \\\\\\ \cfrac{53.5}{x}=\cfrac{4}{3}\implies 53.5(3)=4x\implies \cfrac{53.5(3)}{4}=x\implies 40.1 \approx x[/tex]
