m∠DEA=70. So, the correct answer is:B. 70
To determine m∠DEA, we need to use the fact that the angles in a triangle add up to 180 .
Since ∠BCA=70 and ∠CDE and ∠DEA form a linear pair, the sum of their measures is
m∠CDE+m∠DEA=180
Given that m∠BCA=70 , we can find
m∠CDE as follows:
m∠CDE=180 −m∠BCA
m∠CDE=180 −70
m∠CDE=110
Now, since ∠CDE and ∠DEA form a linear pair,
m∠CDE+m∠DEA=180 . We know
m∠CDE=110 , so:
110 +m∠DEA=180
Now, solve for
m∠DEA:
m∠DEA=180 −110
m∠DEA=70
So, the correct answer is:B. 70
Question
What is m∠DEA ? given BCA= 70
A. 20º
B. 70º
C. 90º
D. 180º