How many lines does the Mexico City subway have?

The Mexico City metro has 12 lines, each with a distinctive number, letter, and color. Lines 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, and B are formed by pneumatic rolling trains.

How many lines does the Mexico City subway have?
Mexico City subway. Photo by Alejandro / Unsplash