Using Le Chatelier's principle, we know that the reactions will always be looking for equilibrium, so if we change something in the equation, the reaction will try to counterbalance that change in some possible ways.
1. SO2 is added:
In this case we have more reactant being added, so if we add more of it, the reaction will tend to form more product, therefore shifting the reaction to the right
2. SO3 is removed:
Same principle as the one said before, we have less product now, so the reaction will try to use more reactant and form more products, shifting the reaction to the right
3. Pressure is reduced:
Here is a little bit different, when we have pressure change in a reaction, the shift usually goes to the side with more moles (pressure reduced) or fewer moles (pressure is increased), in our case, we have the reaction shifting to the left, because we have more moles in the reactants side.
4. Temperature is reduced:
In endothermic and exothermic reactions, we can see temperature like reactant or product, in our case we have temperature in the product side, therefore we have an exothermic reaction, since we are reducing the amount of heat in the product side, the reaction will shift to the right, releasing more heat.