Pls help me with this question and if you don't know, pls don't answer. thank you!

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 weight of an object in the water is 7% of its weight out of the water. what is the weight of a 652g object in the water?

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years