A group of friends were at the restaurant. When the bill of 175 dollars came, two people left before the bill was paid. This resulted in the payment of 10 dollar extra by the remaining individuals. How many people were in the group at first?

N = number of people originally

175/n + 10 = 175 / (n-2)

(175+10n) / n = 175 / (n-2)

Cross multiply: (n-2) (175+10n) = 175n

10n^2 - 20n + 175n - 350 = 175n

Subtract 175n: 10n^2 - 20n-350=0

Divide: n^2-2n-35=0

Factor: (n-7) (n+5) = 0

Solutions are - 5 and 7, but the only plausible answer is 7 people at first