After having a discount of 10%, we have to pay the net price: 220x90%= 198
But you have to pay 10.5% service charge, that means the service charge is 198x10.5%= 20.79
And finally you have to pay: 198+20.79= 218.79
Hope it is helpful
You just had to distribute it 25b-5z=5(5b-1z)