This is not a hard question, for the y-axis (frequency density), the graph didn't show you the numbers like the x-axis, but you can figure out the numbers by looking at the table. For example, the table said, "when the time is 30-40 the frequency is 35." When you look at the graph and look for the time range of 30 to 40, you will find that the frequency density is at its highest point, which is 35. It is 7-blocks high, which means that one block on the y-axis is 5.
Now for the answer: For the first missing number -- 15, because it is 3-blocks high and 5*3=15. For the second missing number -- 25, because it is 5-blocks high and 5*5=25.
I might explain better if I am using a graph, if you don't understand, just ask.