Answer:
score = 825
Explanation:
we first need to find z-score for exam A:
z = (x - υ) / σ
where x is observed value, υ is the mean and σ is the standard deviation.
For A:
z = (x - υ) / σ
= (390 - 300) / 40 = 2.25.
we need him to get z-score of 2.25 on exam B. his score is x.
2.25 = (x - 600) / 100
225 = x - 600
x = 825.
so he needs to score 825 on exam B to do equivalently well as on exam A.