Iwasn't at school when they were teaching theoretical and experimental experimental. can someone explain how it works and give me an example?

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 longer leg of a 30° 60° 90° triangle is 16 times square root of three how long is a shorter leg

Aline passes through 3,7 and 6,9 what equation represents the line