area of triangle = 1/2 * base * height
what we know:
area of triangle = 120
height = 15
now we just substitute it in:
120 = 1/2 * base * 15
dividing by something is the same as multiplying by its reciprocal, so:
120 * 2 = base * 15
240 / 15 = base
16 = base
so, your base is 16 inches.
