State the nth term of the following sequence: 3, 7, 11, 15, 19

Start by labelling each term, e.g. 3 is the 1st, 7 is the second etc

Find the difference between each term, in this case +4 so we know our nth term will start with 4n 

Now we substitute in the number for n, we usually use the 1st term since it's easy multiplying by 1. Doing 4x1 gives 4 however our first term is 3, so to get from 4 to 3 we need to -1 making our nth term 4n-1

Test this rule out on at least one other term to check so substituting in 2 we get 4(2)-1=7

The rule works so our nth term is 4n-1