The ratio between what harry pays to what his dad pays is given as 2:3.
We know that harry's dad paid £52.2, therefore, we can use cross multiplication to find the amount that Harry paid as follows:
harry paid = 52.2 * (2/3) = £34.8
The total cost of the meal would be the addition of what they both paid, this means that:
total cost of meal = 52.2 + 34.8 = £87