Answer:
x = 35
Step-by-step explanation:
the 3 angles lie on a straight line and sum to 180° , that is
40 + 2x + 30 + 40 = 180
110 + 2x = 180 ( subtract 110 from both sides )
2x = 70 ( divide both sides by 2 )
x = 35
Opposite angles of an inscribed quadrilateral are supplementary, so it is true that ...
... B. m∠A + m∠C = m∠B + m∠D . . . . . = 180°
