Answer
$\angle C = 106˚$
Work Step by Step
Since $\square ABCD$ is a parallelogram, this means that $DA$ and $BC$ are parallel to each other and therefore $\angle A + \angle B = 180˚$
$\angle A = 2x + 6$
$\angle B = x + 24$
1. Solve for $x$ using the formula: $\angle A + \angle B = 180˚$
$(2x+6) + (x+24) = 180˚$
$3x + 30 = 180$
$3x = 150$
$x = 50$
2. Apply the one of the properties of quadrilaterals, congruent angles. This property specifically states that opposite angles are equal to each other in a parallelogram. Therefore $\angle A = \angle C$ and now we have to solve for $\angle A$.
Substitute the $x$ into the $\angle A$ equation.
$\angle A = \angle C = (2x+6)$
$\angle A = \angle C = 2(50)+6$
$\angle A = \angle C = 100+6$
$\angle A = \angle C = 106˚$
