One equivalent function would be 27^x.
These questions should be asked more clearly.
If 3% is the standard deviation of the average then a 1% decrease in score is a z=-1/3, which is small in absolute value, so we can't reject the claim. In this interpretation we'd answer: -0.33, no.
But if we'll assume 3% is the standard deviation of the individual samples, it's a different story. We use percent as our unit. The standard deviation of the average is
.
So we get a z (really a t) here of
![z = \dfrac{86 - 87}{0.55} = -1.8](https://tex.z-dn.net/?f=%20z%20%3D%20%5Cdfrac%7B86%20-%2087%7D%7B0.55%7D%20%3D%20-1.8%20)
That's kinda borderline, a one sided t test with 29 dfs will give about the same probability as the normal distribution for a tail z=1.8, p=.036 aka p=3.6%. Typically we'd choose a 1% or 5% rejection threshold before we started; this one is in between.
There were 45 people
12n=540
$540 divided by the 12$ per person is 45
540/12=45
Two equations two unknowns
1. 3a + 6s = 60
2. 5a + 3s = 44
solve for a in 1, a = (60 - 6s)/3 = 20 - 2s
substitute into 2
5(20 - 2s) + 3s = 44
solve for s
s = 8
substitute in 1
a = 4
You look at the decimal place next to the hundredth one. In this case, it’s 4 so you round down
18.19 is the answer