Which is a run-on sentence? Two hydrogen atoms and one oxygen atom compose
each molecule of water.
Halocarbons contribute to the loss of ozone in Earth's
atmosphere, so many countries have banned them.
A vertical garden, or green wall, is a wall covered
with vegetation, vertical gardens are gaining
popularity around the world.

The last sentence, “A vertical garden, or green wall, is a wall covered
with vegetation, vertical gardens are gaining
popularity around the world” is a run-on sentence.

There is a comma splice between “vegetation” and “vertical,” which makes the sentence a run-on sentence. To fix it, we could put a semicolon in place of the comma, and the sentence would not be a run-on anymore.

Since it's a quadrilateral, the measures of the angles have to add up to 360. First, subtract 216 (108×2) from 360 to get 144. Now divide 144 by 4 since you have 4x's that must add to 144. When you do the math, you'll find x=36. So the answer is A.