Alright, so here, you have to multiply base times height then divide it by two. So it will be 15 1/4in X 18in = 274 2/4 in². Then, you divide it by two which will give you 137 2/8 in². In a more simplified version, the answer will be 137 1/4 in²

dmp29

The formula for a triangle's area is ( base x height x 1/2 )