HELP 30 Points ANy wrong/bad answers will be deleted by one of my moderator friends.

Find the value of the variable and the length of each secant segment.

7x+8y=-18, 4x-9y=-3 solve the system of equations

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