What is the solution to Three-fourths a greater-than negative 16? a greater-than negative 21 and one-third a less-than negative 21 and one-third a greater-than 21 and one-third a less-than 21 and one-third

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