Answer: 7.8
Step-by-step explanation: Rounding off to one decimal place, the number after the decimal happens to be 7 i.e. 7.7... look out for the next number next to seven which happens to be another 7.
Since the next 7 is more than 5, by law you round it off to 1 and add to the first seven.
Hence our answer becomes 7.8