Jill has 8.75. jack has three times as much as jill, but he spent 5.00 to buy a book. how much money does jack have ?

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