Let the legs of the triangle be a and b, and the hypotenuse c.
Your first instinct might tell you to use the Pythagorean theorem to go about solving this because

. This works, but it is slow.
The fastest way to solve this is to recognize that the right triangle is a special triangle where the ratio of the sides are 3:4:5. This means that if the legs are 9 and 12, then the hypotenuse is 15 because 3*3 is 9, 3*4 is 12, and 3*5 is 15.
Rounded to the nearest tenth the number doesn't change Fam <span />
The appropriate algebraic equation is 2x = 3/4. To solve this for x, multiply both sides of this equation by (1/2), obtaining x = (1/2)(3/4) = 3/8 (answer)