well, what's the diffrence from 5/4 to 3/8?
[tex]\bf \cfrac{5}{4}-\cfrac{3}{8}\qquad \stackrel{\textit{LCD is 8 clearly}}{\implies }\qquad \cfrac{10-3}{8}\implies \cfrac{7}{8}[/tex]
so, if we take 5/4 to be the 100%, what is 7/8 off of it in percentage anyway?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
\frac{5}{4}&100\\\\
\frac{7}{8}&x
\end{array}\implies \cfrac{\quad \frac{5}{4}\quad }{\frac{7}{8}}=\cfrac{100}{x}\implies \cfrac{5}{4}\cdot \cfrac{8}{7}=\cfrac{100}{x}
\\\\\\
\cfrac{40}{28}=\cfrac{100}{x}\implies x=\cfrac{28\cdot 100}{40}[/tex]
