Rubbing the balloon on you hair, the hair causes electrons to be added to the balloon. Hence, the balloon would have excesses electrons.
Hence charge on the balloon is negative.
The effect of the silk is to remove electrons, so when the glass rod is rubbed with silk, the silk remove electrons from the glass rod. Hence, since the rod has lossed electrons, it would then be positively charged.
Hence charge on the glass is positive.
