Because the quadrilateral is inscribed in a circle, the opposite angles will add up to 180°. Because of this, we can set up this equation:
2x + 9 + 3x + 1 = 180
Now, we can solve for x. First, we should combine like terms. Now, the equation is:
5x + 10 = 180.
Now, we need to get x on its own side. We do this by subtracting 10 from both sides.
5x = 170.
Finally, we can divide both sides by 5 to figure out what x is.
x = 34
In order to finish the problem, we just need to substitute this back into the expression for a.
2*34 + 9 = 68 + 9 = 77, so angle a is 77°.
