Angle A is 73 degrees.
This can be found by using the values for both angles and setting them equal to 180. Since they are alternating interior angles of intersections of parallel lines, they must equal 180.
6x - 35 + 3x + 53 = 180
9x + 18 = 180
9x = 162
x = 18
Since x = 18 we can place that into the equation for angle A in order to find it's value alone.
6x - 35
6(18) - 35
108 - 35
73