To determine the score the student needs on the fifth test to achieve an average of 80 across five tests, we'll follow these steps:

Step 1: Calculate the total points needed for an average of 80.

The average for five tests should be 80. Therefore, the total points needed is:

$\text{Total Points Needed} = 80 \times 5 = 400$

Step 2: Calculate the total points earned from the first four tests.

The scores for the first four tests are 63, 72, 88, and 91. We need to find the sum of these scores:

$\text{Sum of First Four Scores} = 63 + 72 + 88 + 91 = 314$

Step 3: Determine the required score on the fifth test.

Let the score on the fifth test be $x$. Then, the equation to satisfy the desired total of 400 points is:

$314 + x = 400$

Solve for $x$:

$x = 400 - 314 = 86$

Thus, the student needs to score 86 on the fifth test to achieve an average of 80. The correct answer is:

G. 86

Would you like any more details or have any other questions?

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Here are 5 related questions that might interest you:

1. What would the student's average be if they scored 90 on the fifth test instead?
2. If the student wanted an average of 85, what score would they need on the fifth test?
3. How would the required score change if the student had one additional test to improve the average?
4. If the student scored a 70 on the fifth test, what would their final average be?
5. How many points would the student need to score on the next two tests to raise their average to 90?

Tip: When working with averages, multiplying the desired average by the number of items gives you the total needed.