Lincoln Elementary School has 120 students. Of these 120 students, $\frac{2}{5}$ ride the bus to school and $\frac{5}{12}$ have a parent drive them to school. If the rest of the students walk to school, what fraction of students walk to school?
I want to find the fraction of students who walk to school, so I need to subtract the fractions of students who ride the bus or have a parent drive them from the total fraction of 1. To do this, I need to find a common denominator for the fractions $\frac{2}{5}$, $\frac{5}{12}$, and 1. The lowest common denominator for these fractions is 60, so I will rewrite them with this denominator. $\frac{2}{5} = \frac{24}{60}$, $\frac{5}{12} = \frac{25}{60}$, and 1 = $\frac{60}{60}$. Now I can subtract the fractions of students who ride the bus or have a parent drive them from the total fraction of 1. $\frac{60}{60} - \frac{24}{60} - \frac{25}{60} = \frac{11}{60}$. This means that $\frac{11}{60}$ of the students walk to school. 