$\displaystyle\frac{{15}}{{500}}=\frac{{3}}{{100}}\usepackage{cmbright}\Huge\$ and $\displaystyle\frac{{18}}{{400}}=\frac{{9}}{{200}}\usepackage{cmbright}\Huge\$ . Because $\displaystyle\frac{{3}}{{100}}\ne\frac{{9}}{{200}}\usepackage{cmbright}\Huge\$ , the ratios that describe the situations are not equivalent fractions. The question asked which museum has the same ratio of guides to students. Because $\displaystyle\frac{{15}}{{500}}=\frac{{9}}{{300}}\usepackage{cmbright}\Huge\$ , the correct answer is the Silver City Art Museum.