A textbook problem, a textbook solution
Let t=M-N
Then M=(2013-3t)/(t-1)
One gets M as positive integer for t= 2, 3,4,6,7,11, 16 and 31; producing 8 possible couples for (M,N): (2007,2005), (1002,999), (667,663), (399,393), (332,325,) (198,187), (131,115), (64,33)
Edited on May 16, 2015, 4:13 pm