Trapezoid midsegment justification

Author:
David
Topic:
Trapezoid
There are two triangles ABC and DEF. EF is parallel to AC and DF is parallel to AB. GH is the midsegment of DEF and IJ is the midsegment of ABC. How can we use these two triangles to show that the midsegment of a trapezoid is the average of the lengths of the bases and parallel to both bases.