Puzzle is a set of gray ropes knotted together that form a map of MIT main campus. Seven red strings are attached at various points with numbers encoded on them using the method described on the khipu wikipedia page. It looks like this:
Basically, this encoding method uses three types of knots, overhand knots, long knots (like an overhand knot with multiple turns), and figure-eight knots. All non-ones-digits are represented by a series of close together overhand knots with a larger gap between the digits, and ones digits are represented by long knots with a number of turns equal to the value of the digit (so an 8 would have 8 turns, etc). Zeros are represented by the lack of a knot in the relevant location, which can be differentiated from just a gap between digits because the gap is twice as large as a normal gap between two digits.
For example, the number 834 would be encoded like so:
where the single o's are overhand knots, and the 4 o's together represent a single knot with four turns.
Each of the seven red strings represents a room number on MIT campus. The place where the string is attached to the map gives the building number, and the number encoded on the string is the classroom number within that building. So for example, to represent 10-250, a red string would be tied to the gray ropes where building 10 would be, and the string has the number "250" encoded on it.
Once the room numbers have been decoded, solvers must go to campus and find a red string outside of each listed classroom with another number encoded on it. These strings are alphanumerically encoded (i.e. A->1, B->2, etc), so each string gives a letter.
The list of room numbers is as follows, with the encoded letter found at each location listed in parentheses:
When the letters are ordered by the building number they were found in, they read out the answer, BUFFALO.