For problem number 1, I'll give you a hint: the domain is all real numbers except one, and the range is all real numbers except one.
For problem number 2, you should recheck your answers. If you substitute into , what you will get is , which is a number, not an interval. For the interval questions, you are missing some intervals. Sometimes you will not be able to write the answer as a single interval, and you will have to write it as a union of intervals, for example: (0, 1) U (3, 4) consists of all numbers that are either between 0 and 1 or between 3 and 4. For the sake of your questions, the notation (0, 1); (3, 4) would probably also be appropriate.
Finally, there is an interval on which the graph is constant.
For problem number 3, the composition f(g(x)) is correct, however, you have computed that composition incorrectly. You are not multiplying the functions together, but you are taking the output from one function (g) and using it as input for the other function (f).
For problem number 4, I'll get you started. The data points are (4, 650) and (8, 400).