Answer:
121°
Step-by-step explanation:
Seeing as how lines DA and CB are parallel, as well as DC and AB, we can say that this is a parallelogram. We are given the opposite angles. Opposite angles of a parallelogram are equal to each other. We need to solve for x.
9x+40=12x+13
Subtract 9x and 13 from both sides.
27=3x
Divide both sides by 3.
9=x.
Now plug in 9 for every x in the measure of angle B.
(12(9)+13)°
(108+13)°
= 121°
