Answer :
[tex] \frac{7}{21} = \frac{12}{yards} \\ \\ 7*yards=21*12 \\ \\ 7yards=252 \\ \\ yards=36[/tex]
21 yards = 7 quilts
21 yards ÷ 7 quilts = 3 yards per quilt
3 yards × 12 quilts = 36 yards
36 yards of material would be required to make 12 quilts.