If ABC is a triangle in which DE ‖ BC and AD ∶ DB = 9 ∶ 8, then DE : BC is _________.

9 : 17 9 : 15 8 : 17 9 : 13

9 : 17

In triangle ABC, AD/DB = 9/8 = \(\frac{ AD }{AB}\) = \(\frac{ DE }{BC}\)  = \(\frac{ 9 }{9 + 8}\) = \(\frac{ DE }{BC}\)  =  \(\frac{ 9 }{17}\) = \(\frac{ DE }{BC}\)  The ratio = 9 : 17