She has 1,244 yards.
Each keychain needs 3.5 yards.
She can make:
[tex]1244\text{ yards}\cdot\frac{1\text{ keychain}}{3.5\text{ yards}}=355.42\text{ keychains}[/tex]If we round, we get that she can make 355 keychains.
If she sells them at 2.50 a piece, she will get:
[tex]355\text{ keychains}\cdot\frac{2.50\text{ dollars}}{1\text{ keychain}}=887.50\text{ dollars}[/tex]She will make 877.50 dollars.