<h3>hello!</h3>
First, let's check how many 7th grade students take the bus.
On the graph, find "7th grade"
There are 90 7th grade students taking the bus.
Same with the 8th grade:-
120 students
How many 7th & 8th grade students take the bus?
The sum of the 7th grade students & the 8th grade students is your answer.
So, add:-


<h3>note:-</h3>
Hope everything is clear; if you need any explanation/clarification, kindly let me know, and I'll comment and/or edit my answer :)