tolong jawabin soal ini no 13 dan 14 saya lupa caranya

13. bc²=16²+12²
     bc= 20
bc/ac=db/dc
20/ac=16/12
16ac=240
ac=15 (c)

12^2 = 16 x AD
144/16 = AD
9 cm  = AD
AC = √9x(9+16) = √9 x 25 = √225 = 15 cm