65(7) = 455 sit-ups during a 7 day period
My answer would be letter (D.)
It means that you have to get a good one for the two weeks and you then have to get the two
Start from the right side and say
6 times 8 is 48 carry the four, 6 times 9 is 54 add your 4 you carried that gives you 58, carry your five and say 6 times one is 6 add your carried 5 and you get 1188