Final answer:
By calculating the measures of the angles within triangle ABC, we can determine that the longest side of the triangle is opposite the largest angle.
Step-by-step explanation:
The question pertains to angles in a triangle and finding the longest side. In triangle ABC, with BC extended through C to D, angle BCD is given as 30° and angle ACD as 110°.
From the geometry, one can deduce that angle ACB is 40° (since 110° + 30° + angle ACB = 180° for a straight line at point C).
Furthermore, in triangle ABC, the sum of the angles will be 180°.
Therefore, if we subtract angles ABC and ACB from 180°, we can find angle BAC. Using the knowledge that the longest side of a triangle is opposite the largest angle,
we can then determine which side of triangle ABC is the longest based on the angle measures.