The answer is A) 28
Set up a proportion based on the triangle side lengths. I chose to put the smaller ones over the bigger ones:
[tex] \frac{6}{42} = \frac{32-x}{x} [/tex]
Then cross multiply to get 1344-42x = 6x
Add 42x to both sides to isolate the x changing the equation to 13444 = 48x
Divide both sides by 48 to get x = 28