so from 18 to 15.125 is 2.875, namely their difference.
now, if we take 15.125 to be the 100%, what is 2.875 off of it in percentage?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
15.125&100\\
2.875&p
\end{array}\implies \cfrac{15.125}{2.875}=\cfrac{100}{p}\implies p=\cfrac{2.875\cdot 100}{15.125}[/tex]
