I need help with this as well

Mr and mrs smith buy tickets for themselves and their four children. the cost of an adult ticket is ? 6 more than the adult ticket. the total cost of the six tickets is ? 40.50 work out the cost of an adult ticket. in your working let c be the cost of the child ticket and a be the cost of the adult ticket.

Sasha drank 8 bottles of water everyday for a week. how many bottles of water did she drink in total?

Including 6% sales tax, an inn charges $135.68 per night. find the inns nightly cost