9.999 round off to the nearest 1000​

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Pls the last one and it has to be like number 6

Jared had 3/7 of the minutes on a family phone plan remaining for the month. the plan is shared by 2 people. if divided equally what portion of the minutes remaining on the phone plan would be avalible for each person