1. 1 solution see graph 1 (-5,0)
2. 1 solution see graph 2 (1.842,8.842)
3. 1 solution see graph 3 (12,6)
These are all straight lines so they are only going to intersect once. Unless you have something like a square or cube where you get a curve in the line, it will always only have one solution.
Hope that helps.
