The order of the scores is not important.

 

Mary's best grade is better than Nick's best grade.

However, Mary's second grade is lower than Nick's second grade.

So overall, their means are equal.

 

Mary's grades are half of Nick's grades,

so her mean will be half of Nick's mean.

 

Mary's grades look to be half as good as Nick's,

but since her grades are out of 10, not 20, they are actually equal.

 

Nick's first grade is out of 20, and his second grade is out of 10.

So his 20 is twice as significant as his 0.

Mary's grades are both out of 10, and therefore of equal significance.

 

This time, Nick's 0 is more important than his 10.