Answer
The class width is 5.
Work Step by Step
The class width for grouped data is found by looking at the lower class limits of two consecutive classes (rows) on a frequency distribution table and then finding the difference between those two lower class limits.
For instance, the first two classes (rows) of data have lower class limits of 0 and 5. The difference is 5 - 0 = 5. This is the class width.
For this problem you just see how much it increases by.