She can make 12 eye glass cases.
Out of one yard, you can make 4 eye glasses cases since she’s using a quarter of a yard for each.
Let’s say x is the amount of cases.
1/4*x =3
Since 1 yard is equal to 4 cases, (4 quarters make up 1) you would do 4 times 3, which is 12.
1/4*12=3
Hope that helps!!!