I'm really stuck on this and any help would be much appreciated

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

How do you find the area of a triangle

Henry is an avid reader, he devours 90 pages in half an hour how many pages has henry read per minute?