Answer:
Amount each friend pays for the gift = $20
Step-by-step explanation:
Market price of a gift = $70
The store manager takes $10 off the market price.
Marked down amount = $10
New cost price = Marked price - Marked down amount 
The cost of the gift is divided among three friends.
This means that the cost of gift which is $60 is divided by three to get each one's contribution in the gift.
∴ Amount each friend pays for the gift 
Answer:
We end up with our original number
Step-by-step explanation:
Let x be our number
We increase by 100
increase = old number * 100%
increase = x*1
increase = x
New number = old number + increase
= x+x
=2x
Now we decrease by 50%
decrease = number *50%
= 2x*.5
=x
Final number = new number - decrease
= 2x-x
=x
The correct answer is letter C.
The reason is because there are 12 cake donuts out of the 36 total. This is a simple ratio of 1 to 3. This means one out of every 3 people would get a cake donut. If there are 12 people, this is 4 groups of 3, so one person from each group of 3 is 4 people.