Answer:
A. 47°
Step-by-step explanation:
ΔABC is an isosceles triangles as shown in the picture with two congruent (equal) sides. When the sides are congruent, then the corresponding angles are also congruent. Since ∠A = 4x + 7 and ∠B = 5x - 3, these two expressions are equal to each other:
4x + 7 = 5x - 3
Add 3 to both sides: 4x + 7 + 3 = 5x - 3 + 3 or 4x + 10 = 5x
Subtract 4x from both sides: 4x + 10 - 4x = 5x - 4x or 10 = x
Since x = 10, solve for m∠B: 5(10) - 3 = 50 - 3 = 47°
