Leah cannot be claimed as a dependent under a multiple support agreement because she provides 52% of her own support.
According to the given information, Leah provides 52% of her own support using funds borrowed from a mortgage on her home, while her sons furnish the rest. In order to be claimed as a dependent under a multiple support agreement, Leah needs to provide less than 50% of her own support. Since she provides 52% of her own support, it means that Leah cannot be claimed as a dependent under a multiple support agreement.