How to see if a point is differentiable at a point

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.

Which of the following statement about pascal's triangle are true?

Solve this equation using substitution. {4x + y = −2} {4x + 6y = 44}