Answer
Find out the how many comic books does Jim have.
To proof
Let us assume that comic books Jim have be u.
Let us assume that comic books Charlie have be v .
Let us assume that comic books bob have be w .
As given
jim has three times as many comic books as Charlie
thus
u = 3v
Charlie has two thirds as many books bob.
Thus
bob has 27 books .
i.e w = 27
Put this in the equation
Solving
v = 18
thus
comic books Charlie has be 18 .
Put v = 18 in the u = 3v
u = 3 × 18
= 54
comic books Jim has be 54 .
Hence proved