The mean of n numbers is the sum of the numbers divided by n.
You have a mean score of 84 after taking 5 tests. Let x be the sum of scores.

You scored a total of 420 points on five tests.
You need to have a mean score of 85 after taking 6 tests. Let y be the score you need to obtain. Your total score on 6 tests is 420+y.

You need to score 90 points on the sixth test.
The answer:
the valid proof is <span>Amanda's.
</span><span>Statement Justification ∠1 + ∠4 = 180°
Definition of Supplementary
Angles ∠3 + ∠4 = 180°
Definition of Supplementary Angles
∠1 + ∠4 = ∠3 + ∠4
Transitive Property of Equality ∠1 ≅ ∠3 </span>
I think the answer is
42.5
not sure but hope this helps