Consider the Lines Perpendicular to a Transversal Theorem
We cannot say anything. Explanation: See solution.
Practice makes perfect
It sure looks like a, and b are parallel as do c and d. However, we cannot be sure of this. For example, if we are going to be sure that c and d are parallel, they would have to be perpendicular to the same line. We would need to know that they are perpendicular to a or b.
The same reasoning applies to determining if a and b are parallel. But we do not know this. Since we have no information about the unknown angles, the figure could be as follows:
