Take x as the number of middle school students. According to the statement, the ratio of elementary students to middle school students is 2:1, which means that for every x middle school students there are 2x elementary students.
The sum of elementary and middle school students is 27. Which means that the sum of x and 2x is 27:
[tex]\begin{gathered} 2x+x=27 \\ 3x=27 \\ x=\frac{27}{3} \\ x=9 \end{gathered}[/tex]The number of elementary school students is 2x:
[tex]2x=2(9)=18[/tex]There are 18 elementary students on the bus 5.
