Please someone help me with these questions

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

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year

Solve 3x-18=2y and 5x-6y=6 by elimination show work