First, identify the locations of the pictures, and fill in the question marks with the buliding numbers from which the pictures were taken.
In RSA (Rivest's office is one of the images), you decrypt a string c by raising it to the d'th power and reducing modulo n. Examining the strings you get as binary numbers and looking at each byte's ASCII value (after zero-filling the left side if needed to get an integral number of bytes), they spell the strings shown below each set of numbers. As confirmation that you are performing this step correctly, c0, d0 and n0 decrypt to the string "Answer".
Here are the three other sets of numbers, and what they decrypt to:
c1: 299360858976878
d1: 178945
n1: 321507024399947
decrypted message: 98292145614711 = "Yellow"
c2: 383385080453079
d2: 137101
n2: 1453072661514151
decrypted message: 1399813490 = "Sour"
c3: 993361527620159366809
d3: 32131511
n3: 5557146835944315965981
decrypted message: 1409984002076480594290 = "Lousy Car"
What's Yellow, a Lousy Car, and Sour? A LEMON!
2006 MIT Mystery Hunt