Asail is in the form of a right triangle that is four times as high as it is wide. the sail is made from 18 square meters of material. what is it's height?

Let the width (base) be w.  Then the height is 4w.  The area of this right triangle is then (base)(height)/2, which must equal 18 square meters.

Substituting the base and height:

(w)(4w)=18 square meters

Thus, 4w^2=18 square meters.  Solving for w, w^2=18/4, or w=+9 meters.  The height is 4 times that:  h = 4(9 meters) = 36 meters.