The answer is the option C and the option D, which are:
C. Double the number of pages in the book.
D. The age of my friend.
The explanation for this problem is shown below:
By definition, a variable is an unkown quantity. In the Option A the quantity is given: 
seconds in a minute. In the option B you know the quantity too, which is 
years old. But the option C and the option D does not give any quantity, you don't know the number of pages in the book or the age of the friend yet. Therefore, the answer is the options C and D.
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weekly income y:
y = 10x
where x is number of hours worked per week
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domain: x >= 0 hours
range: y >= 0 dollars
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Solve and graph linear equations:
https://sooeet.com/math/linear-equation-solver.php
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Sin = opposite/hypothenuse
Given opposite = 16
Hypothenuse = ?
Use Pythagorean theorem to find hypothenuse
12^2 + 16^2 = h^2
144 + 256 = h^2
h^2 = 400, h = 20
You know hypothenuse is 20
Opposite/hypothenuse
Solution: 16/20
Simplify if you need to (4/5)
Answer: IM pretty sure your correct
Step-by-step explanation:
