A function is when an x value doesn't have more that one y value (y can have more than one x value, though). On the teachers and pets one, Ms. Valverde has two pets, so that doesn't count. On the shapes one, the orange square is pointing to another orange square and a triangle, so that doesn't count. The last one has 7 equaling to 12 and 13, so that doesn't count. The one with the months doesn't have any x values with more than one y value, so it is a function.
