What are the changing variables in, costant variables, formula, and whether or not its direct or inverse for boyle's, charles', gay-lussac and combined laws

Boyle's Law: The relationship between a gas' volume and pressure, where the temperature is assumed to be constant. The relationship is an inverse one and the formula is P₁V₁ = P₂V₂

Charles' Law: The relationship between a gas' volume and temperature, where pressure is assumed to be constant. The relationship is a linear one and the formula is V₁ : T₁ = V₂ : T₂.

Gay-Lussac's Law: The relationship between temperature and pressure, where volume is assumed to be constant. The relationship is a linear one and the formula is P₁ : T₁ = P₂ : T₂.

Combined Law: Boyle's, Charles', and Gay-Lussac's laws all combined, where all the variables are changing. I'm unsure of what the relationship is but the formula is P₁V₁/T₁ = P₂V₂/T₂.

*Note: The subscripts just indicate the original amount to the new amounts.