It's x=xo+vot+.5at^2, x or y, but when you use y be sure to use -9.8 for a.
You screwed up your original formula, but you did it right in the problem. That drives me crazy. xD
Not knowing the problem, and a quick look over the second part looks right. Looks okay.
What is this for? I know it's a test, but what level/course of education?
Edit: I'm going to take a guess and say that #1 is that you are given a velocity vector, and you are supposed to determine how long it takes for it to travel -10m in the y and then find how long it went in the x during that time. I agree with your answers.