Is fire a solid a liquid or a gas?

Neither. Fire is a process, not a physical object. When you burn wood, the reaction is actually happening between the wood and oxygen in the air to form carbon dioxide and water vapor. Wood is a solid, but oxygen, carbon dioxide and water vapor are all gases. If you have a gas powered stove, you are burning a gas called methane (or maybe propane). There everything is a gas. So fire is not a solid or a gas, but it is the name for a type of reaction that can involve both solids and gases (and liquids too in fact).

If you mean the flame that you see as being fire you would be wrong. Flame is the result of fire.Fire is the combination of heat and a combustible material. A good example of this is the burning cigarette.