To find your missing angle:
180-126 = 54
so 9x must equal 54
54= 9x
6 = x
9n + 6 = 456
9n = 456 - 6
9n = 450
n = 450/9
n = 50
I believe this is the answer, though i'm not sure.
Hi there!

We can solve for x knowing that the sum of interior angles in a triangle is 180°.
The square at the bottom indicates a right angle, or 90°. Therefore:
180 = 90 + x + (x + 10)
Combine like terms:
180 = 100 + 2x
Subtract 100 from both sides:
180 - 100 = 2x
80 = 2x
Divide both sides by 2:
x = 40.
Answer:
Step-by-step explanation: