Question

Enter the number that belongs in D= ?

Answer 1

∠ D = 80°

Explanation:

Δ BCA and Δ DCE are congruent ( SAS postulate )

Thus corresponding angles are congruent, thus

∠ D = ∠ B

The sum of the 3 angles in a triangle = 180°

Subtract the sum of the 2 angles in Δ ABC from 180° to find ∠ B

∠ B = 180° - (30 + 70)° = 180° - 100° = 80°, then

∠ D = 80°

Answer 2

Answer:

A triangles angles add up to 180 degrees, and along with that the triangles are directly corresponding or are the same as each other meaning the angles are mirrored.

With that in mind we subtract the angles we have from 180 to find the missing angle.

180-70-30
180-100
80

D=80 degrees