I need to understand part b.
how did they get n(p)
in other words, how did they go from
p = F(n(p)) ......to n(p)
see the attachment!
That's just the quadractic equation. Let x be the $\displaystyle p^{th}$ percentile
so p=F(x) or $\displaystyle p=2(x+{1\over x} -2)$
multiply by x and create a quad equation
$\displaystyle px=2(x^2+1 -2x)$
$\displaystyle x^2 -(2+{p\over 2})x+1=0$
NOW solve for x and discard the bad solution.