Respuesta :

well the formula is : b1+b2/2 (h)

so the height would be solved as : 
13.5 = 3+6/2 (h)
13.5 = 9/2 (h)
h = (13.5)/(9/2)
h = (13.5) x (2/9)  *reciprocal*
h = (27) / (9)
h = 3