posted by Samay
You are pulling a raft up a river. You can make 15 miles each day. Each night, while you are asleep, however, the current pushes the raft 3 miles back downstream. If you set out on Tuesday to get to a town 85 miles upstream, on which day will you arrive?
each day you make 12 miles
After 6 days you have gone 72 miles
on the 7th day you'd make it to mile 87, so you're done.
so, what day is that?