You know the area, so you can use the area formula A = 1/2(a+b) (a and b being the parallel sides AB and CD)
So, set 32.5 = 1/2 (AB +CD)
substitute --> 32.5 = 1/2( x+(x+1) )
simplify --> 32.5 = (2x+1)/2
simplify again --> 65 = 2x +1 --> 64 =2x --> 32 =x
Now that you have x, you can substitute it into the formula for your height (x-1) to get 31