Mr and Mrs Thomas buy tickets for themselves and their four children The cost of an adult ticket is £7 more than the cost of a child ticket. The total cost of the six tickets is £86. Work out the cost of an adult ticket.

Let's call the prices a and c, a for adult ...

The cost of an adult ticket is £7 more than the cost of a child ticket:

a = 7 + c

The total cost of the six tickets is £86.

86 = 2a + 4c

c = a-7

86 = 2a + 4 (a-7) = 6a - 28

114 = 6a

a = 19

Answer: £19

Check:

That implies c=12.

2a+4c = 2 (19) + 4 (12) = 38 + 48 = 86, good