Answer:
x = 17.6
Explanation:
We know that a quadrilateral will have a total of 360 degrees. We can create an expression and solve for x.
5x + 7x + 3x + 6 + 90 = 360
~Combine like terms
15x + 96 = 360
~Subtract 96 to both sides
15x = 264
~Divide 15 to both sides
x = 17.6
Best of Luck!