Really, we don't need to use that much math--we can use logic instead. Since the two congruent sides must be longer than 30in, the total has to be greater than 60in (the longest side plus the congruent sides.) So for our answer, we want the smallest total that is above sixty, which in this case is 72.44in.
Hope I helped, and let me know if you have any questions :) I can explain the real math if you want, it was just unnecessary here.
