BITSAT 2012 Paper

xy – 12x – 12y = 0 ⇒ (x – 12) (y – 12) = 144
Now 144 can be factorised into two factors x and y where x ≤ y and the factors are
(1, 144), (2, 72), (3, 48), (4, 36), (6, 24), (8, 18), (9, 16), (12, 12).
Thus there are eight solutions.