Parallelogram Area Formula:
Area= base * height
A= bh
Trapezoid Area Formula:
Area= 1/2height * (base1 + base2)
A= 1/2h(b1 + b2)
OR
A= (b1 + b2)/2 * h
This formula can be written and done a couple different ways, and the result will be the same. Note that base1 may be the top edge of a trapezoid and base2 may be the bottom edge. If you have some specific examples, feel free to post them.
Hope this helps a bit! :)