If Mr. Jones served 85 hot dogs to 50 people the proportion of hot dogs is:
If he expects 68 people at the fall picnic, the amount of hot dogs he will need is the number of people multiplied by this proportion:
Answer
The proportion that could be used to find how many hot dogs Mr. Jones will need for the fall picnic is 85/50
He will need 115.6 hot dogs (since the number of hot dogs is a whole number, He will have to buy 116 hot dogs)