Answer:
x = 17
Explanation:
∠ DCE = ∠ ACE ( vertically opposite angles )
The sum of the 3 angles in a triangle = 180° , then
∠ DCE = 180° - (100 +x) = 180 - 100 - x = 80 - x
∠ ACE = 180 - (49 + 4x) = 180 - 49 - 4x = 131 - 4x
Equating the 2 angles
80 - x = 131 - 4x ( add 4x to both sides )
80 + 3x = 131 ( subtract 80 from both sides )
3x = 51 ( divide both sides by 3 )
x = 17