a mean of μ = 78 points with σ = 9. She collects a sample mean of M = 84 for app users. What is the null hypothesis, in both words and symbols?

M ≤ μ (=78)

Here μ denotes the means of the population

And, M denotes the sample mean

Step-by-step explanation:

The computation of the  null hypothesis, in both words and symbols is given below:

Null Hypothesis(H0) is

M ≤ μ (=78)

This means that the study application does not improve the grades

Also

Alternative hypothesis (H1): M> μ

Here μ denotes the means of the population

And, M denotes the sample mean

thats not a system of equations, that is a solution

i think the answer is d im not sure