Edit: Wait, you posted this in the Ext 2 forum. I tried interpreting questions myself and had little to no luck. I need my teacher to explain stuff when it's time to learn how to do them.
I've always hated permutations and combinations. This is what I did to get through:
1. Arrangements in a line - n!
2. Arrangements in a circle - (n-1)!
2. a) Arrangements of beads on a bracelet - (n-1)!/2 because when the bracelet is flipped you get similar permutations
3. Ways of being chosen in a specific order - nPr or n!/(n-r)!
4. Ways of being chosen in any random order - nCr
5. 'And' means multiply
6. 'Or' means plus
7. Repeated letters in making "words", where k is the amount of letters, is n!/k!
8. Repetitions in general: Arrange the repetitions individually, then arrange the entire thing together
9. Consider cases seperately if need be - this is hardest to do.. Seeing as you posted this in the 4U forum
10. Probability is always given P = Favourable outcomes / Total outcomes
E.g. to explain 8.
A group of 8 people are to be seated in a line. If Anna and John wish to sit together, how many ways is this possible?
Arrange Anna and John together - Anna and John can sit in 2! ways
Then, treat them as one person, i.e. AnnaJohn. Then, there are 6 other people. Meaning, 7 people need to be arranged in a line. There are 7! ways of doing this.
Therefore, arrangements = 2! * 7!