Answer:
b. Invalid, because the sample may not be representative of the population.
Step-by-step explanation:
A sample of around 10% of the population is needed to be representative.
In this question:
We have a population of 500,000, and a sample of 10,000.
10,000/500,000 = 1/50 = 0.02 = 2% of the population, so not representative, and option b is correct.
We can compare by converting Johnny's reading time into the same unit of Jacky's, hours.
There are 60 minutes in an hour, so use this:

15 < 20, so Johnny read faster. This is 5 pages faster per hour than Jacky.
Supplementary means it adds up to 180 degrees.
So if one side is 31 degrees, you would need to subtract that from 180 to find the other side.
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180 - 31 = 149
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The other angle would be 149 degrees.
Here is one <span>Jake’s salary depends on the number of hours he works.
The independent variable is the number of hours and the dependent variable is salary.
Let x = the number of hours worked
Let y = Jake's salary
The set of ordered pairs {(1, 10), (2, 20), (3, 30), (4, 40), (5, 50)} can be used to represent
the function, assuming Jake earns $10 per hour.
</span>
To do this make x and y equal 0, y-intercept is at x=0, and x-intercept is at y=0:
x-intercept:
2x+7(0) = -14
2x = -14
x = -7
y-intercept:
2(0) + 7y = -14
7y = -14
y = -2