(3) 8
Step-by-step explanation:
Note that ∆ADE is similar to ∆ABC. As such, the ratios of their legs are equal. Also note that AD = AB + BD.
BC/AB = DE/AD
BC/10 = 12/(10 + 5) = 12/15 = 4/5
or
BC = 10(4/5) = 8
Answer:
x=18
180 - 106 = 74
180 - 68 - 74 = 38
