we know that
To make a costume,
if Rachel uses 6 yards of material and------> 3 yards of trim.
for 48 yards of material----------------------------> X?
X=48*3/6--------> X=24 yards of trim
Let
a--------> [yards of trim for several costumes]
b--------> [yards of material for several costumes]
c--------> [yards of trim for one costume]
d-------->[yards of material for one costume]
the rule is--------> a=b*c/d
the answer is
24 yards of trim