Area of triangle = 0.5 * height * base
if you know any two variable you can get the third from the equation
in here we have area = 27 feet ^2
and base = 12 feet
so by sub. we can get height as follow :
area = 0.5 * h* b
27 = 0.5 * 12 * h
27 = 6 h
so , h= 4.5 feet
