The two lines with arrows are parallel, which means angles A and B are supplementary.
So we have
A + B = 180º
(6x - 35)º + (3x + 53)º = 180º
(9x + 18)º = 180º
(9x)º = 162º
x = 18
This means angle A has measure
A = (6x - 35)º = 73º
