Question

2) Christmas is on its way, so the price of a box of Thornton's chocolates has been increased

Answer 1

15% as a decimal is 0.15
Our regular cost of chocolates is 1.0
New cost is 1.0 + 0.15 = 1.15
1.15 x 17.25 = 19.8375
In the states we round to the hundredth for cost, so it would be £19.84

Alternate method: calculate 0.15 of 17.25 and add that to 17.25
0.15 x 17.25 = 2.5875
17.25 + 2.5875 = 19.8375