About 6,271 people had viewed the video once it had been online for 20 days. The correct option is C.
<h3>What is exponential equation?</h3>
Exponential equation is the equation in which the exponent or part of exponents used as variables.

where, x is the number of days, given that x = 20
Putting the values in the equation

Thus, the correct option is C, 6,271.
Learn more about exponential equation
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Answer:
The inequality symbol is incorrect because she can spend up to and including $65.
The expression 5. 50b + 7. 5 is correct because $5. 50 per book is 5. 50b and that is added to the shipping fee of $7. 50 to determine the total purchase price.
Explanation:
The inequality should be 5.50b + 7.5 ≤ 65 because she can use less than $65 or all $65 to spend on books.
Also, the shipping fee is for all the books she buys combined, not for each individual book so the left side of the inequality should read 5.50b + 7.5.