can someone explain this?

Question

The following is a frequency data set for test scores in a small class. Construct a cumulative frequency plot displaying data. Then describe the graph in a sentence or two.

test scores:
40-49:1
50-59:2
60-69:2
70-79:7
80-89:9
90-99:5

Answer 1

cumulative:
49 1
59 3
69 5
79 12
89 21
99 30

so graph that. Now describe it.