#13 would be 100%.
#15 would be $9.90.
#17 would be 408.
#19 would be 27840.
#21 would be 26.
Sorry for the late reply.
Answer:
Option B. 
Step-by-step explanation:
Let
b------> the number of buses
we know that
-----> inequality that represent the situation
Solve for b
Answer:
what to do here I don't know sorry
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The predicted value of hardness at 37 hours is 243.87 and an 85% confidence interval for the mean hardness is (242.12, 245.61). At 41 hours, the predicted hardness is 252 and an 85% confidence interval for mean hardness is (249.83, 254.18). The confidence interval for X is equals to 41 which is wider because the value 41 is farther away from the sample mean X than is 37. As an outcome, the standard error for the prediction is larger.
3x8 is 24 plus 4 is 28
7x1 is 7 plus 2 is 9
9+28 is 37
