A=72m b1+b2=30m what is the height?

a=(b1+b2)h. i knoe how to solve for the area but i do not knoe how to find the height or bases of a tzoid. i havent come a cross a problem that i had to solve for the bases yet, buht i donnot knoe how to do either. helpp!! explain in full detail cos i qet confused EASILY.