Correct answer is option E
The area of the triangle DFH is 10 and there are 4 small triangles within this area, since all the triangles are congruent and equilateral, it means the area of 4 small triangles is equal to 10
Area of DFH = Area of 4 small triangles = 10

To find the area of AFK which consist of 25 small triangles is to first divide 25 triangles by 4 triangles to find out how many 4 triangles AFK contains.
25/4 = 6.25

This means the big triangle (AFK) contains 6 (four triangles) and a quarter (of four triangles)
Area of AFK = area of four triangles number of four triangles in the big triangle
= 10 6.25
= 62.5
Therefore, the area of AFK is 62.5)