3 - 6 + 12 - 24 + 48 - 96 = -63 or D
it is going in a pattern; the next number is always the last number but multiplied by two, and the signs are alternating between - and +
3 x 2 = 6
6 x 2 = 12
12 x 2 = 24
24 x 2 = 48
48 x 2 = 96
add and subtract everything and you get -63