Check out the image attachment for one way to draw this problem out. Notice how angles AEC and DEB are vertical angles, so that means they are congruent angles
(measure of angle AEC) = (measure of angle DEB)
6x + 20 = 10x
6x + 20-6x = 10x-6x ... subtract 6x from both sides
20 = 4x
4x = 20
4x/4 = 20/4 ... divide both sides by 4
x = 5
The value of x is 5.
Let's check the answer
6x + 20 = 10x
6*5 + 20 = 10*5 ... replace every x with 5
30+20 = 50
50 = 50
We have confirmed the answer.