I really don't get his

Answer:
40.32 sqcm
Step-by-step explanation:
For two similar polygons, ratio of corresponding sides are equal.
Here, ratio of breadth = 4.8/4 = 1.2
So, length of the larger rectangle = 7 * 1.2 = 8.4
So, area of the larger triangle = 4.8 * 8.4 sqcm = 40.32 sqcm