Final answer:
The total cost for Mr and Mrs Miles and their 3 children to travel is £10.50.
Step-by-step explanation:
To calculate the cost of the trip for Mr and Mrs Miles and their 3 children, we need to consider that children travel at half price. The adult fare is £3, so the children's fare would be £3/2 = £1.50 each.
Therefore, the total cost for the 3 children would be £1.50 x 3 = £4.50.
Adding this to the cost for Mr and Mrs Miles, which is £3 + £3 = £6, the total cost for the entire family to travel would be £6 + £4.50 = £10.5.