Trapezoid Midsegment Properties
The
midsegment of a trapezoid is the line that connects the midpoints of the two nonparallel sides of the trapezoid.
The midsegment of a trapezoid has two special properties:
 The midsegment of a trapezoid is parallel to each base.
 The length of the midsegment of a trapezoid is equal to half the sum of the lengths of its bases.
Find a, x and y. 

x = 55º
y + 120º = 180º. Therefore y = 60º