I think I’m wrong on this question , can I get help .

What is the rule for reflection across the y axis

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

Combine like terms to make a simpler expression 3z+z