the equation for the area of a right triangle is 1/2 x base x height. therefore on the first triangle i would assume 4 and 3 are the base and the height. therefore the hypotenuse would be 5 because a^2 + b^2 = c^2. a and b are the base and the height and c is the hypotenuse. so if you multiply 3 by 4,3 and 5. youre new base and height would be 12 and 9 and the hypotenuse would be 15. if you plug 12 and 9 (the base and the height) into the formula for the area of a right triangle (1/2 x base x height) the area of the new triangle would be 54. hope this helps!!