The correct answer is 17.5.
Because they share a common angle at the top, we know that we can create a proportion using similar sides.
[tex] \frac{Outside LEFT}{Bottom LEFT} = \frac{Outside RIGHT}{Bottom RIGHT} [/tex]
[tex] \frac{16}{10} = \frac{28}{x} [/tex]
Now we can cross multiply to solve.
28*10 = 16*x
280 = 16x
17.5 = x
