Solve worksheet please a lot of points

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.

Solve the equation -9p - 17 =10 a -3 b. 16 c. 18 d -16

What is the value of x when x + 7 = 21?