From the question, we have
GST on ticket of Rs.80=18% of 80=18/100×80=Rs.14.40
GST on ticket of Rs.120=28% of 120=28/100×120=Rs.33.60
So,
The difference between both GST =33.60−14.40=Rs.19.20
Thus, the extra GST Asharaf paid for the ticket was Rs.19.20