In the following figure, AF is the perpendicular-bisector of BD, AD = 15, and DF = 13. Find AB + BF

Answer 1

since AF is the perpendicular bisector of BD, therefore BF=FD. since DF=FD=13, BF=13
now, if you draw this figure, you will see that you form a right triangle (AFD) when you connect A and D,, connecting A and B, you form another right triangle,,
since they share a common height, and BF=FD, it follows that AD=AB=15
therefore,
13 + 15 = 28

hope this helps~ :)