To solve #V = lwh# for #w# we need to divide each side of the equation by #color(red)(l)color(blue)(h)#
#V/(color(red)(l)color(blue)(h)) = (lwh)/(color(red)(l)color(blue)(h))#
#V/(color(red)(l)color(blue)(h)) = (color(red)(cancel(color(black)(l)))wcolor(bue)(cancel(color(black)(h))))/(cancel(color(red)(l))cancel(color(blue)(h)))#
#V/(lh) = w#
#w = V/(lh)#