for an isosceles trapezoid, the angles on a straight line are equal
so,
Angle R = Angle Q
so since angklw R = 80 degrees,
Angle Q = 80 degrees.
Also recall,
Angle S = Angle T
to find Angle S,
Angle S = (360 - (80 + 80))/2
Angle S = (360 - 160)/2
Angle S = 200/2
Angle S = 100 degrees
since Angle S = Angle T
therefore,
Angle T = 100 degrees