Hey gulrez. Firstly, you observe that there are two similar triangles in the diagram.
1) ABC ||| DBE [equiangular, corresponding angles of parallel lines are equal)
2) DBC ||| FBE [same reason as above]
Now, AB/DB = AC/DE = CB/BE = 3/2 [for ABC ||| DBE] (AB = 15, DB = 10, thus AB/DB = 3/2)
Also, DB/FB = DC/FE = CB/BE = 3/2 [for DBC ||| FBE] (CB/BE = 3/2 as shown above)
Thus, DB/FB = 3/2
But, DB = 10
Therefore, 10/FB = 3/2
10/(3/2) = FB
Thus, FB = 20/3 cm (or 6 and 2/3 cm) #
Correct to 2dp, FB = 6.67 cm
