Answer:
10
Explanation:
the two triangles formed from c are similar which means the sides are proportional
the proportion of one length of a side of a triangle to a similar side of the other triangle is the same as another side to its corresponding side of the other triangle. god im bad explaining stuff
anyway 2 is to 8 what 2.5 is to length BC. 2/8 = 2.5/x
-crossmultiplyyy
2*x = 2.5*8
2x = 20
2x/2 = 20/2
x = 10