the equation for finding the area of one triangle is A=1/2(B)(H)
because we have two triangles, we do not need to divide the answer by two.
That being said, 8 times 12 is 96.
By installing a sprinkler for every 10 sq ft. of land we divide that by 10 and get 9.6
Because the decimal value is above 5, my answer would be that you need 10 sprinklers.