If x=7, determine which lines must be parallel?

Answer: All the lines which are parallel to Y-axis including Y-axis must be parallel to the line x=7.

Explanation:

We can understand it by drawing the line x=7 on the graph.

In the graph, it has shown that x=7 is parallel to Y-axis.

And if we talk about a set of lines x=n, where n is a real number then these lines are parallel to y-axis.

since, we know that if one line is parallel to another line and that line is also parallel to a third line then these three lines must be parallel.

so we can say that, All lines which are parallel to y-axis as well as y-axis are parallel to x=7.