On Monday, 169 students went on a field trip to the zoo. All 4 buses were filled and 9 students had to travel in cars. How many students were in each bus

X (the number of students on the bus)

so

4x=169-9

you get that equation since the number of total students minus the number of students who had to ride in a car now solve

4x=160

you get this by subtracting nine

now divide by four

x=40