Answer
$a = 20$
Work Step by Step
We are given that the diagram is that of a parallelogram.
Opposite angles of a parallelogram are congruent. We can set the two opposite angles equal to one another:
$6a + 10 = 130$
Subtract $10$ from each side of the equation to isolate constants to one side of the equation:
$6a = 120$
Divide both sides of the equation by $6$ to solve for $a$:
$a = 20$
