You are right. 5 is correct.
A) to find the difference you have to subtract one from the other (53-(-41)=91)
b) 15
This is a proportion problem that involves cross-multiplication
Set your problem up like so:

=

Now cross multiply
2,000 x 3 = 6,000
now you're left with 5x = 6,000
Now divide by 5 on both sides
Answer is 1,200
Males have chromosome pairs of (XY) and Females have chromosome pairs of (XX)