Elevation in boiling point is a colligative property. A colligative property depends upon the number of solute molecules irrespective of nature or molecular weight etc.
As all the given solutes (in all the three solutions) are non ionic (will not dissociate into ions) so with same molality (moles per unit Kg) they will have same number of molecules. And thus all the three aqueous solutions will have same boiling point.
