Solve the following math problem step by step. The last line of your response should be of the form Answer: \boxed{$Answer} where $Answer is the answer to the problem.

<image>ABCD is a trapezoid.
If $m\angle ABC = 4x + 11$ and $m\angle DAB = 2x + 33$, find the value of $x$ so that ABCD is isosceles.