Hello!
We know that the sum of all angles in a triangle is 180 degrees. This can be represented by the following formula:
(angle 1) + (angle 2) + (angle 3) = 180
Insert all known values and variables of triangle ABC into the formula above:
30 + (80 + y) + y = 180
Simplify and combine like terms:
30 + 80 + y + y = 180
110 + 2y = 180
Now subtract 110 from both sides of the equation:
2y = 70
Divide both sides by 2:
y = 35
We have now proven that Y is equal to 35 degrees. Using the known value of Y, we can find the value of X using the same formula as above. Begin by inserting all known values and variables of triangle BCD:
y + y + x = 180
(35) + (35) + x = 180
Combine like terms:
70 + x = 180
Subtract 70 from both sides of the equation:
x = 110
We have now proven that X is equal to 110 degrees. Therefore, considering the known values of X and Y, the answer to this problem is C.
I hope this helps!