No problem. The first thing to know is that a solution is a type of mixture. Take two different things and mix. Done. Mixture complete. You can have a heterogeneous mixture, which does not have an even distribution of materials. You can have a homogeneous mixture which does have an even distribution. As for a homogeneous solution, the easiest way to describe that is a REALLY well-mixed homogeneous solution.
The above states that pretty much anything can be a mixture. If it is mixed enough it can become evenly mixed; it's possible for a lot of things to be in a solution, and it doesn't matter if they're liquids, solids, or gases. I'll give an example of each for your question.
1. Gas in a solid -- hydrogen being dissolved into palladium. I suppose whipped cream could work too.
2. Solid in a solid -- bronze (copper and tin) or stainless steel (steel and chromium).
3. Solid in liquid -- sugar or salt water solution.
4. Gas in a gas -- air because it's oxygen, nitrogen, and other gases.