She can make 14 curtains.
There are 3 feet in 1 yard: 7 yards * 3 feet = 21 feet in 7 yards
There are 12 inches in 1 foot: 21 feet * 12 inches = 252 inches in 7 yards
We want to know how many curtains Nancy can with 252 inches of fabric when the curtains are 18 inches long: 252/18 = 14
Nancy can make 14 curtains with 7 yards or 252 inches of fabric.