Given that the mean is $9.5 and the standard deviation is $1.30, the standard error will be given by:
σ/√n
where
σ-standard deviation
n=sample size
thus, we shal have:
1.30/√20
=0.2906
Next we find the margin error
0.2906*2=0.581
thus the confidence interval will be:
(9.5+0.581, 9.5-0.581)
=(10.081,8.919)
8+0.75x=25
0.75x=25(-8)
0.75x=17
17/0.75= 22.666
He can ride a total of 22 rides
Which one do you want to he answered?

now, we get critical points from zeroing out the derivative, and also from zeroing out the denominator, but those at the denominator are critical points where the function is not differentiable, namely a sharp spike or cusp or an asymptote.
so, from zeroing out the derivative we get no critical points there, from the denominator we get x = 8, but can't use it because f(x) is undefined.
therefore, we settle for the endpoints, 4 and 6,
f(4) =3 and f(6) = 7
doing a first-derivative test, we see the slope just goes up at both points and in between, but the highest is f(6), so the absolute maximum is there, while we can take say f(4) as the only minimum and therefore the absolute minumum as well.