these numbers form an addition and subtraction fact family 6,7,13 choose the fact family formed by these numbers a 7+13=20 13+7=20 13-13=0 13-0=13 b 7+0=7 6+0=6 13-0=13 13-13=0 c 7+6=13 6+7=13 13-6=7 13-7=6 c 7+6=13 13=7+6 13-6=7 7=13-6 is it abc or d​