the answer for this is The first eight men spent rs 80 and the ninth man spent rs x.
The sum that all 9 men spent was 80+x
The average of all nine men was rs
The equation comes from this sentence:
The ninth man spent rs 4 more than the average of all of them.
Clear of fractions by multiplying through by 9:
Solution: rs 14.50
Average = =
The ninth man spent rs 14.5 and the others spent rs 10. So
he spent rs 4 more than what the others spent.