if we take 31 to be the 100%, what is 28 off of it in percentage?
[tex]\bf \begin{array}{ccll} amount&\%\\ \cline{1-2} 31&100\\ 28&x \end{array}\implies \cfrac{31}{28}=\cfrac{100}{x}\implies 31x=2800\implies x=\cfrac{2800}{31} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ ~\hfill x\approx 90.32~\hfill[/tex]
