I need to find the relationship between A and B, where

$\displaystyle A = \frac{{{L_2} - {L_1}}}{{{L_1}\left( {{t_2} - {t_1}} \right)}}

$ and $\displaystyle B = \frac{{{V_2} - {V_1}}}{{{V_1}\left( {{t_2} - {t_1}} \right)}}$

I'm assuming I need to make $\displaystyle {V_1} = {L_1}{W_1}{H_1}\,\,\,{\rm{and}}\,\,\,{V_2} = {L_2}{W_2}{H_2}$

So basically, how do I get

$\displaystyle \frac{{{L_2} - {L_1}}}{{{L_1}\left( {{t_2} - {t_1}} \right)}}$ out of $\displaystyle \frac{{{L_2}{W_2}{H_2} - {L_1}{W_1}{H_1}}}{{{L_1}{W_1}{H_1}\left( {{t_2} - {t_1}} \right)}}$ ?

I've only gotten so far:

$\displaystyle {W_1}{H_1}B = \frac{{{L_2}{W_2}{H_2} - {L_1}{W_1}{H_1}}}{{{L_1}\left( {{t_2} - {t_1}} \right)}}$

and I can't figure out how to extract $\displaystyle {{L_2} - {L_1}}$ from the numerator on the right side of the equation.

Is this even possible? Am I going about this problem incorrectly?