please can some1 help me wiv this question

in a set of 30 people, 21 prefer tea, 9 prefer coffee and 16 have sugar in their tea

if P = {people who prefer tea}

Q = {people who prefer coffee}

R = {people who take sugar}

calculate

(i) [P]

(ii) [R]

heres another similar question i am having problems with

in a set of 35 people, 23 are wearing hats, 25 are wearing gloves and 30 are wearing either hats or gloves.

how many people are wearing:

(i) both hat and gloves

(ii) neither hat or gloves

i know these questions have something to do with set theory and Venn diagrams please would you be able to explain how you found the answers thanks.