Short answer: 98
Remark
when you have an average of 71, it's like saying that you took 4 quizzes and got 71 on all of them.
Step One
Find the total point count for the 4 quizzes.
T_4 = 71 * 4 = 284
Step Two
Create an equation that will give you the necessary point count to average 86.
284 + 5*x = 86 * 9
Why did we do this? It is because you have 9 quizzes altogether. All nine must be something that gives a point count of 86 on each quiz. You have to put together 9 such quizzes with a total count of 774.
Step three
Solve the equation.
284 + 5x = 774 Subtract 284 from both sides.
5x = 774 - 284
5x = 490 Divide by 5
x = 490/5
x = 98
You must get an average of 98 on the next 5 quizzes
Answer: 98 <<<<<