Take into account that the sum of the interior angles in the given figure is equal to 360°. Then, you have:
m
replace the algebraic expressions into the previous equation and consider
mm
mm
2m2(6x + 20) + 2(4x + 10) = 360
12x + 40 + 8x + 20 = 360
20x + 60 = 360
20x = 360 - 60
20x = 300
x = 300/20
x = 15
next, replace x=15 into the expression for mm
Hence, the measure of angle A is 110°
