There are 5 equations and 6 unknowns. This means we can define 5 variables in terms of the remaining one.
Let's use a as the variable defining the other variables.
b=4a/3; c=b/5=(4a/3)/5=4a/15; d=3c/4=a/5; e=d/2=a/10; f=4e=2a/5.
def=(a/5)(a/10)(2a/5)=a^3/125;
abc=a(4a/3)(4a/15)=16a^3/45;
def/abc=45/(16*125)=9/(16*25)=9/400, answer d.