Challenge offer! Can anyone answer to these questions.?

Question

1. There are 20 questions in a mathematical test. 7 marks are awarded for each question answered incorrect. No mark is given for each question left unanswered.
If a pupil scores 100 marks what is the no. of questions he left unanswered.

2. In a party three types of bottled drinks-mineral water, coca-cola and fresh orange juice were served.
A bottle of mineral water is to be shared by 2 people.
A bottle of fresh juice is to be shared by 4 people.
Give that 91 bottles of drink were consumed and that each person had consumed 1 share of each type of drive find the total number of people present at the party.

Please find the answer and tell as possible as you can!
It's for my homework, So please answer.
Atleast answer any one.

Answer 1

I'm not sure how to answer the first question, but mainly because I don't think I understand it. How many marks does someone get for answering correctly? Anyway, for the second, If cokes are one serving, mineral water 2 servings, and juice 4 servings, the equation is:

x + 1/2x + 1/4x = 91

Multiply by 4 to clear the denominators.

4x + 2x + x = 364

7x = 364

x = 52 People

4x = 52 Cokes
2x = 26 Mineral Water
x = 13 Juice

Answer 2

The first question is incomplete. How many points are awarded for a correct answer? The equation will be X * right + (-7 * wrong) = 100, where X is the points for a right answer and right + wrong < 20.