Question

In the following diagram, BC is parallel to DE.
What is x?

Answer 1

x is 21

Explanation:

add 54 and 105, then subtract it by 180 and you get 21.

Answer 2

21

Explanation:

Using alternate interior angles, we can conclude that angle C is equal to X (the 3rd, unmarked angle in the center triangle)

To find that 3rd angle, we can do 180 - 105 - 54. This is because all angles in a triangle must equal 180. Using this, we find that angle C is equal to 21. By the law, X must also equal 21.