Answer:
30 students
Explanation:
First, we need to find exactly how many students went to school by car and how many went on the bus.
To do this, we simply multiply the fraction of students that used each transportation method by the total number of students.

So, 90 students went to school by car.

So, 120 students went to school on the bus.
The number of students that walked to school is the same as the number of students who didn't go in a car or on the bus, so to find the number of students that walked to school, we can subtract the number of students that went by car and on the bus from the total number of students.
