Answer :
x-jugs
y-glasses
6x+12y=21l
x=5y
6(5y)+12y=21l
x=5y
30y+12y=21l
x=5y
42y=21l
x=5y
1l=2y
x=5y
x=12,5 l
y=2,5 l
y-glasses
6x+12y=21l
x=5y
6(5y)+12y=21l
x=5y
30y+12y=21l
x=5y
42y=21l
x=5y
1l=2y
x=5y
x=12,5 l
y=2,5 l