What must be true for a ratio of two measurements to be a conversion factor

The heaviest 16% of all men in weight weigh more than how many pounds ?

F(x)=x/2-2 and g(x)=2x^2+x-3 find (f+g)(x)

Astick 2 m long is placed vertically at point b. the top of the stick is in line with the top of a tree as seen from point a, which is 3 m from the stick and 30 m from the tree. how tall is the tree?