Each image consists of two superimposed sections of MIT blueprints. Each image contains either a + or a - in the superimposed section as well as two notes of the form "Let - = #" where # is some digit each by a different building. For each image, identify the two room numbers where the + or - sign is, insert the digit (in the note by each building) in place of the dash, and then add or subtract.

Besides the last two, the resulting numeric string can be interpreted as a room number using the same mechanism where one of the digits is actually a dash. In particular, each string can be interpreted as a room number of a room on campus that is named after a person. Using the number that the dash replaces as an index into the last name of the room gives the message FATHER OF GPS. The last two blueprints give the single digits 8 and 9. This is an enumeration for the answer. The clue is thus FATHER OF GPS (8 9) cluing BRADFORD PARKINSON.