I think it’s ordinary annuity
Answer:

Step-by-step explanation:






There won't be any change in the total mass of the atoms involved in a chemical reaction. According to the law of conservation of mass; it states that mass can neither be created nor destroyed in a chemical reaction. So, when atoms participate in a chemical reaction they might displace with other reactants but the total mass will remain the same.
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RainbowSalt2222 ☔
So, since averages are defined as:

So, since P are the total number of elements and P_k is the P_kth student. This is saying if we sum over each student's score and divide it by the number of students, we should get P, which is true.
So, using that logic, the other class can be represented as:

We can take both of these equations and multiply them by N:


So, if we want to find the average of this we should add both our equations then divide by P+N, which is the number of all the students.

To make this simpler we can replace our LHS with 86, since that's the average of both classes combined.

Simplified we would have P/N=3/8.
Answer:
this right answer for this would be D