The domain is the set of all x for which T(x) is defined. If you have a digraph, it's all the values in the form x = ... that have a value y = ....

"Domain = the x-coordinate"... almost.

Range, on the other hand, is the set of all values in the form T(x) for some x in the domain of T.

Similarly, in a digraph, there will be an x value for each y value.

Are you familiar with onto and one-to-one?

Now that you know what domain/range are, can you do these problems, or at least attempt them? If you show your thought process on these in the future, we can better help you find out where you're going wrong rather than just feeding you the answers...