First it would be far better to type the problems in yourself rather than link to a word document- they are notorious for having viruses. Many people will not open "Word" attachements. I did only because I have very strong virus protection on this computer.
Second, the problem asks you to determine how many solutions a system of equations has without solving the system- yet you have solved the first system. That said, your answers to the first two questions are correct and your method is good. Why did you not do the same with the third problem?