Fifth graders read 68, which is easy to see. Fourth graders read between 48 and 52, the bar appears to be directly in the middle of the two lines, so we say they read 50. Third graders read between 40 and 44, again the bar appears to be directly in the middle so we say they read 42.
If you have any questions about the problem, you should ask your teachers or parents, trust me, you will appreciate their help later. Also, the bar graph is adding the total books read so you just look at the bar graph for anything between two seperate, values subtract these two values by each other.
