7/5=x/3 solve proportion

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.

Iknow its nothing to do with education, but what type of thing should i wrote here? ? : ) its for mcdonald's btw.

What is 0.000008 meters in scientific notation