Respuesta :
Tess is correct about figuring 10% but he added 2 of them together which is like adding 10% +10% which is 20% not 15%.
he should have taken 1/2 of the 4.60 for 5% since 5 is half of 10
half of 4.60 = 2.30
then add that to the 4.60
4.60 +2.30 = 6.90 is 15%