Given that ABCD is a parallelogram and ∠B = 80°. What can you conclude about the other angles of the parallelogram?

We know that,

Opposite angles in a parallelogram are equal.

∴ ∠D = ∠B = 80°

Since, ∠A = ∠C = x (let)

We know that,

Sum of angles in a parallelogram is equal to 360°.

⇒ ∠A + ∠B + ∠C + ∠D = 360°

⇒ x + 80° + x + 80° = 360°

⇒ 2x + 160° = 360°

⇒ 2x = 200°

⇒ x = 100°

Hence, ∠A = ∠C = 100° and ∠D = 80°.