What's The value of x

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

Describe how making an ‘and’ compound sentence effects your solution set

Susie wants to take her friend out for lunch.she wants to spend $9.75 each person. how much will she spend in all.