All three of the integers can be written in terms of a: since they are consecutive evens and we know the order, b = a + 2, and c = a + 4. Thus, we can simplify c − b − a: (a + 4) − (a + 2) − a = a + 4 − a − 2 − a = −a + 2 = 2 − a Since a must be a positive even number and none of the answer choices are much below zero, try a = 2 : 2 − a = 2 − 2 = 0, choice (D). Using a slightly larger value of a = 4: 2 − a = 2 − 4 = −2 As a gets bigger, 2 − a gets smaller–smaller than any of the choices. (D) must be correct.