If E= Emily's homeroom class students, and S = Santiago's homeroom class students then
[tex]\begin{gathered} 0.75E=15 \\ \frac{2}{3}S=12 \\ \\ E=\frac{15}{0.75}=20 \\ S=\frac{12\cdot3}{2}=18 \\ \\ \text{ Then Emily's class has more students!} \end{gathered}[/tex]