Here are the solutions to each of the questions in the image:

7. What percent of 60 is 15?

$\text{Percent} = \left(\frac{15}{60}\right) \times 100 = 25\%$

8. 9 is 45% of what number?

$\text{Number} = \frac{9}{0.45} = 20$

9. What number is 12% of 72?

$\text{Number} = 0.12 \times 72 = 8.64$

10. What percent of $12 is $9?

$\text{Percent} = \left(\frac{9}{12}\right) \times 100 = 75\%$

11. 75 is 20% of what number?

$\text{Number} = \frac{75}{0.2} = 375$

12. What number is 40% of 80?

$\text{Number} = 0.4 \times 80 = 32$

13. $3 is what percent of $40?

$\text{Percent} = \left(\frac{3}{40}\right) \times 100 = 7.5\%$

14. 12.5% of what number is 24?

$\text{Number} = \frac{24}{0.125} = 192$

15. 8.2% of 50 is what number?

$\text{Number} = 0.082 \times 50 = 4.1$

16. What percent of 300 is 0.6?

$\text{Percent} = \left(\frac{0.6}{300}\right) \times 100 = 0.2\%$

17. 45 is 150% of what number?

$\text{Number} = \frac{45}{1.5} = 30$

18. What percent of 25 is 30?

$\text{Percent} = \left(\frac{30}{25}\right) \times 100 = 120\%$

19. What number is 0.5% of 8?

$\text{Number} = 0.005 \times 8 = 0.04$

20. 6% of what number is $10 \frac{1}{2} = 10.5$?

$\text{Number} = \frac{10.5}{0.06} = 175$

21. A paperback book originally priced at $12.50 is on sale for $7.50. What percent of the original cost is the sale price?

$\text{Percent} = \left(\frac{7.50}{12.50}\right) \times 100 = 60\%$

Would you like a detailed explanation for any specific question or further clarification?

Related Questions:

1. If $3 is 7.5% of a number, what is the number?
2. What percent of 80 is 64?
3. If 45% of a number is 36, what is the number?
4. Find 12.5% of 256.
5. How much is 0.05% of 10,000?

Tip:

When solving percentage problems, always double-check whether the question asks for "percent of a number" or "what number is a percent of."