Answer:
10 questions with an incorrect answer for both parts
15 questions with a correct answer in only one part
Step-by-step explanation:
Let's call x the number of questions with an incorrect answer for both parts and y the number of questions with only one part of the question correct.
So, the equation that gives us the number of points after 25 rounds is:
100 - x - 0.5y = 82.5
Where: x + y = 25
So, solving for y, we get:
y = 25 - x
Replacing this on the initial equation and solving for x, we get:

Then, the value of y is:

Therefore, the player gets 10 questions with an incorrect answer for both parts and 15 questions with a correct answer in only one part.