Answer:

Explanation:
Opposite angles of an inscribed quadrilateral are supplementary, so ...
m∠A + m∠C = 180°
Substituting the given expressions, we have ...
(3x +6)° + (x+2)° = 180°
4x +8 = 180 . . . . . . collect terms, divide by °
x +2 = 45 . . . . . . . . divide by 4
3x +6 = 135 . . . . . . multiply by 3
This is the value of angle A in degrees, so ...
m∠A = 135°