Step-by-step explanation:
To multiply the fractions, like

Multiply the top,
then multiply the bottom.

Try to use a calculator if you aren't arithmetic heavy, but I suggest you to try to remember them because they are going to be helpful for courses like Algebra, Calculus, Statistics, etc.
To divide fractions, like

You take the top number,

Then you flip the bottom number,

Then multiply the two

And that is your answer. Comment if you need more clarification
8) there are 3 people and each pays 14.68
3•14.68= $ 44.04 was the entire meal
10) 15 oz that he drank+ 20oz that were left= 35 oz were originaly in the container
Density = m/v with mass being in grams and volume in mL......
192 grams/250 mL = 0.768 g/mL
X+y=57
y=x+15
x+x+15=57
2x=42
x=21
y=21+15
y=36
The 4 litres of red has to be 2 parts of the mixture, so each part will be 2 litres. Therefore 3 parts of cream will be 6 litres and the one part of blue will be 2 litres.