New secured 4.5 is the best option
You would first have to find common denominators for the fractions. In this case it would be 10. So your new equation would be 3 5/10 - 2 4/10. Once you do this you can then subtract and solve getting the answer of 1 1/10
She will nee 391 square feet of flooring at $13.59: $5313.69