Answer:
B. 76°
Explanation:
The theorem regarding the angles of parallelograms is that the two sets of opposite angles are congruent. This means that in this parallelogram:
∠A ≅ ∠C
∠B ≅ ∠D
We also know that the sum of all angles in a quadrilateral is equal to 360°.
Let's correlate these assumptions:
∠A + ∠B + ∠C + ∠D = 360°
∠A ≅ ∠C
∠B ≅ ∠D
So through substitution:
∠A + ∠B + ∠A + ∠B = 360°
2(∠A) + 2(∠B) = 360°
We are given:
m∠A = 104°
Now let's insert that in our equation:
2(∠A) + 2(∠B) = 360°
2(104°) + 2(∠B) = 360°
208° + 2(∠B) = 360°
Subtract 208° from both sides of the equation:
208° - 208° + 2(∠B) = 360°- 208°
2(∠B) = 152°
Divide both sides by 2:
2(∠B)/2 = 152°/2
∠B = 76°