Answer:
B. 29º
Explanation:
Given that BCDE is a parallelogram, then
and A, E and D are collinear. Then, angle E inside triangle ABE and angle D inside parallelogram BCDE have the same measure. That is:
(1)
In addition, the sum of internal angles in triangles equals 180º, which implies that:
(2)
If we know that
and
, then
is:
![\angle A = 180^(\circ)-\angle B - \angle E](https://img.qammunity.org/2022/formulas/mathematics/high-school/x0gu9yjon0hayrwhudnwl9fhiei4xddm50.png)
![\angle A = 180^(\circ)-100^(\circ)-51^(\circ)](https://img.qammunity.org/2022/formulas/mathematics/high-school/mabwibguunseeksaxtkx7pt7za0tvyxj8w.png)
![\angle A = 29^(\circ)](https://img.qammunity.org/2022/formulas/mathematics/high-school/dx02gucpt4dardq1exfuu1o3iwheg7rnux.png)
Hence, correct answer is B.