First you need to put everything as 1 unit. I'll convert both to fractions for now.
75% = 3/4
680/1 * 3/4
Cross Multiply
2040/4
Simplify
510
The mayor received 510 votes.
18 bags of sand will be needed
Multiply the fraction by 100%.

For this question it is the difference of two perfect squares. This means your final answer will be (2x - 5)(2x + 5). This answer is not listed so it would be none of the above.
After review, B technically works because it is the difference of two perfect squares. This allows you to take the square root of each term while ignoring the sign and then place that back in with the original sign.
Answer:
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x
- x - 6</h2><h2 />
Step-by-step explanation:

Multiply each term in the first parentheses by each term in the second parentheses ( FOIL)

Calculate the product

Collect like terms

Hope this helps..
Best regards!