Answer:
The top and middle shelves are parallel.
Explanation:
<1 and <5 are corresponding angles.
When two lines are cut by a transversal such that corresponding angles are congruent, the lines are parallel.
If angles 1 and 5 are congruent, the shelves are parallel.
We are given m<5 = 60°.
Also, m<2 = 120°.
Angles 1 and 2 are a linear pair and are supplementary.
The measures of angles 1 and 2 add to 180°.
m<1 + m<2 = 180°
m<1 + 120° = 180°
Subtract 120° from both sides.
m<1 = 60°
m<1 = m<5 = 60°
Since angles 1 and 2 have the same measure, 60°, angles 1 and 2 are congruent.
Answer: The top and middle shelves are parallel.