Given that the two figures are similar, use a scale factor to find the missing length x.

Step-by-step explanation:

Corresponding sides are the key here.  If the figures are similar then their corresponding sides exist in proportion to one another.  Again, corresponding is key when you're trying to find the missing side length.  Set it up as a proportion:

and now all you do is cross multiply:

18x = 1782 so

x = 99

i would say c is the best answer, hope it's right!

good luck! =)

cutie~