@Jennifer62 , if it is just an enquiry, then you don't need to preapprove or decline. Just respond to their message within 24 hours with a yes or no to their reduced rate request. If you agree to the discount, then you will need to send a special offer, which is up to them to accept or not. If you don't agree with the discount but youre still happy to accept them at the normal rate, you can preapprove and it is up to them whether to proceed at the normal rate.
If it is an actual request, then you technically need to accept or decline. However if you don't agree to the reduced rate, then ask them to withdraw their request so you are not penalised for declining. If they don't do this, you can tell them you will accept at the normal rate and if they're not happy with that, it is then up to them to cancel the booking.
By the way, asking for discounts is considered a red flag for hosts because it usually indicates a less than ideal guest.