Venn diagrams, Tables and Trees are equivalent

These 4 possibilities can be represented by the 4 areas on a Venn diagram with two overlapping circles, also by a 2x2 table, and also by a tree with two levels of branching. All 3 views are equivalent. You should use whichever is the most convenient for the problem.

Tables can be easier than Venn diagrams because you can include sums at the end of the rows and columns, which means that you can often just write the values given in the question straight into the table in the correct places, and then do the subtractions in your head to fill the table out.

Trees are especially helpful if there are conditional probabilities involved, as you can write the values from the problem statement straight onto the tree.

If you are filling in a table of 2x2 values, since you know they all add up to 1, you have 3 unknowns, which means you need 3 facts to be able to solve the table completely. Check before you start that you have everything you need. One of the facts migh be disguides, like a statement that the events are independent, or mutually exclusive.

When it comes to 3 events, there are 2^3=8 possibilities. All 3 representations are still valid but a table is a bit more cumbersome, as you have to visualise a 3D table, which you would usually write as two separate tables. A Venn diagram is useful here since 3 overlapping circles can be drawn with all 8 areas available on the picture.

For 4 events there are 2^4=16 areas to show and a Venn diagram cant show this, so you are best with a tree or possibly a table. You shouldn't need to do 4 events in Statistics 1.