the total amount is "x", so, if 22.8 is 58%, "x" is the 100%,
[tex]\bf \begin{array}{ccllll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
22.8&58\\
x&100
\end{array}\implies \cfrac{22.8}{x}=\cfrac{58}{100}\implies \cfrac{22.8\cdot 100}{58}=x[/tex]
