Subtract -3n^2 from -7n^2

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

Find the distance between the pair of points a(-1,8) and b(-8,4)

240 seventh graders and two-thirds of the students participate in after-school activities how many students participate in after-school activities