Answer:
D. 78°
Step-by-step explanation:
ABCD is a parallelogram.
Measures of the opposite angles of a parallelogram are equal.
Therefore,
[tex]3x = x + 52 \\ \\ 3x - x = 52 \\ \\ 2x = 52 \\ \\ x = \frac{52}{2} \\ \\ x = 26 \\ \\ m\angle B = (3x) \degree \\ \\ m\angle B = (3 \times 26) \degree \\ \\ m\angle B = 78\degree[/tex]
