three plate of Momo cos 90 Rupees one plate cost 19/3 which is 30 then 3 bottle of cold drink cost three x 30 which is 90 total is 120 so 10% service search is 120 didvided by 100 multiplied by 10% which is 12 rupees service charge that is 12 divided by 100 x 13 is 1.56 so first year is says that calculate the service to the service charge is 12 rupees and how much is the vat amount is 1.56 as we do 12 divided by 100 multiply by 13 then it says and how much you need to pay so we need to pay 120 + 1.56 which 121.56 thank you