Help please? Test is due tomorrow please help.

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.

When you answer this can you explain

Secant be and cf intersect at point d inside a what is the measure of cde