Mixture or pure substance:
1.water
2.blood
3.the oceans
4.iron
5.brass
6.uranium
7.wine
8.leather
9.table salt (nacl)

Mixture is a system where there are two or more substances which are mixed but not chemically bonded. Pure substance is any substance which is has only one component. Therefore, the following are classified as:

1.water = pure substance
2.blood = mixture
3.the oceans = mixture
4.iron = pure substance
5.brass = mixture
6.uranium = pure substance
7.wine = mixture
8.leather = mixture
9.table salt (NaCl) = pure substance

1. and 2. question: in which equation? or i don't understand you, 3. a), 4. c), 5. c), 6. b), 7. d), 8. d) if small number is underlined(behind symbol) , b) if big number is underlined(in front of symbol)9. what is underlined there? 10. c)