Answer is 19cm
Step by step
We know
Formula for area is A=1/2bh
Area is 256.5
b is 27
Plug these into your formula for Area and solve
256.5 = 1/2 (27) h
256.5 = 13.5 h
Divide both sides by 13.5 to solve for h
256.5/13.5 = 13.5/13.5 h
19 = h
Your height is 19cm