See attached picture for the answers:
The differnce of 2 perfect cubes
remember
a³-b³=(a-b)(a²+ab+b²)
so
The answer is b.
This is because the line is sloping downwards, and so y = -1
The student would earn %86. To calculate percentage you take the amount of questions correct, divide that by the amount of questions given, multiply by 100 and round to the nearest percent.