How to predict the effect of a change in conditions

Question

Using Le Chatelier's Principle to predict the effect of a change in conditions on a chemical equilibrium.

Le Chatelier's Principle

Calculate how the equilibrium of the following reactions will be affected by the changes listed.
____ HI(g) + 2.246 kcal _____ H2 (g) + _____I2 (g)

1) Adding SO3(g)
2) Adding O2(g)
3) Removing SO2(g)
4) Decreasing the pressure