Answer:
DEC = 90*
Explanation:
Ok, well lets list some facts really quick.
Since AB is parallel to CD, and AD is parallel BC, angles A and C are the same, angles B and D are also the same.
Knowing that A and C are the same, C = A, the measurement of angle C is 68*. ( * = degrees)
Since line EC bisects, meaning it splits into two equal parts/measurements, C, the measurement of angle DCE and BCE is both 34*.
How is it 34*, well 68*/2 = 34.
Next, interior angles of triangles on the same line equal to 180* (a straight line).
This means that the measurement of angle B has to equal up to 180* when added with angle A.
To find angle B we do 180* - 68* = 112*.
Thus, angle B equals 112*, because when added with A, it equals 180.
Since angles B and D are the same, angle D is also 112*.
One way to check this is to add up all interior angles in a rectangle (those angles being A, B, C, and D) and they should all add up to 360.
Since line DE bisects angle D, or splits it into two equal parts, angles ADE and CDE equal 56*.
Note: All angles in a triangle add up to 180*.
Since we know angles A and D, we can find angle DEA based on the rule above.
A + ADE + AED = 180*
68 + 56 + AED = 180*
124 + AED = 180
Subtract 124 from both sides to get angle AED
124 + AED = 180
-124 -124
AED = 56*
Now we must find angle CEB.
B + BCE + CEB = 180*
112 + 34 + CEB = 180
146 + CEB = 180*
Subtract 146 from both sides to get CEB
146 + CEB = 180
-146 -146
CEB = 34
Now we can find angle DEC.
AED + CEB + DEC = 180*
56 + 34 + DEC = 180*
90 + DEC = 180*
Subtract 90 from both sides to get DEC
90 + DEC = 180*
-90 -90
DEC = 90*
Answer: DEC = 90*