What would you do if I said I wanted you

Idon’t understand this.. will someone ? will mark brainliest along with 20 points.

Anyone know? is appreciated! will mark brainliest if correct!

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