To calculate the score you need on the third test to maintain an average of 90, we can set up the equation for the average of three test scores.

The formula for the average of three tests is:

$\text{Average} = \frac{\text{Test 1} + \text{Test 2} + \text{Test 3}}{3}$

You want the average to be 90, so we set up the equation:

$90 = \frac{96 + 97 + x}{3}$

where $x$ is the score you need on the third test. Now, let's solve for $x$:

1. Multiply both sides of the equation by 3 to eliminate the denominator: $270 = 96 + 97 + x$

2. Simplify the right-hand side: $270 = 193 + x$

3. Subtract 193 from both sides to isolate $x$: $x = 270 - 193 = 77$

So, you need to score at least 77 on the third test to keep your average at 90.

Would you like more details or clarification on this? Here are 5 related questions you might find useful:

1. How do I calculate the average for more than three tests?
2. What happens if I score higher than 77 on the third test?
3. How does weighting affect my average if the tests have different point values?
4. What if I want to achieve a higher average, like 95? How would I calculate that?
5. How can I track my grades to ensure I meet my goals?

Tip: If you have future tests, it's a good idea to calculate your desired average after each test, so you can stay on track!