Your answer would be x = 12
The triangle sum theorem states that the 3 angles in a triangle equal 180.
Since we have a 90 degree angle shown, we can add it to the other two and set it equal to 180.
30+90+6x-12=180
108+6x=180
6x=72
x=12
THE ANSWER IS B 0 PLS MARK ME BRALIEST