First rewrite this problem as:
#(color(red)(3)/color(green)(4))/(color(blue)(7)/color(orange)(8))#
Now, use this rule for dividing fractions:
#(color(red)(a)/color(green)(b))/(color(blue)(c)/color(orange)(d)) = (color(red)(a) xx color(orange)(d))/(color(green)(b) xx color(blue)(c))#
Substituting gives:
#(color(red)(3)/color(green)(4))/(color(blue)(7)/color(orange)(8)) = (color(red)(3) xx color(orange)(8))/(color(green)(4) xx color(blue)(7)) = 24/28 = (4 xx 6)/(4 xx 7) = (color(red)(cancel(color(black)(4))) xx 6)/(color(red)(cancel(color(black)(4))) xx 7) =#
#6/7#
