Answer:
So then the correct answer is B. $200.
Step-by-step explanation:
Notation
Let X be the average contribution size before John makes his contribution.
Let Y be the total contribution size before John makes his contribution.
Let Z be John's contribution.
We know that for this case $ 75 represent the original average amount before the contribution with 50% increase so we can set up the following equation in order to find the original average amount
And solvong for X we got:
Now we can find the total contribution before the donation with the following proportion:
And then with the formula of average taking in count the 6 values we can find the size of donation Z like this:
So then the correct answer is B. $200.