Answers and explanation .
( cousin needs , im terrible with this kind of stuff)
7. 64% of 75 tiles =
8. 10% of 70 plants=
9. 32% of 25 pages=
10. 85% of 40 emails
11. 72% of 350 friends=
12. 5% of 220 files=
13. 4 students is % of 20 students
17. 4% of days is 56 days
18. 60 minutes is 20% of minutes
19. 80% of games is 32 games
20. 360 kilometers is 24% of kilometers
22. 9 stores is 3% of stores
24. 200 songs, 24 of them are country songs. % of the songs are country
25. sales tax= 7%. amanda paid 35$ in sales tax on a stereo. what was the price of the stereo?
27. monica paid a sales tax of 1.50$ when she bought a helmet. if the sales tax rate was 5% how much did the store charge for the helmet before tax?
28. how many hours per day does becky spend on each activity.
sleep: 40%
school: 25%
eating: 10%
free time: 15%
homework: 10%
school: hours
eating: hours
sleep: hours
homework: hours
free time: hours

There are 3 terms to remember in answering these questions. WHOLE, PART, PERCENTAGE.

Whole is the total amount. 
Part is the portion of the whole
Percentage is usually the rate of the part to the whole.

If the part and percentage is given and we are looking for the whole or total.
Whole = part ÷ percentage of the part

If the whole and percentage of the part is given and we are looking for the part:
Part = whole * percentage of the part

If the part and the whole is given and we are looking for the percentage:
percentage = (part / whole) x 100%

7) 75 * 64% = 48 tiles
8) 70 * 10% = 7 plants
9) 25 * 32% = 8 pages
10) 40 * 85% = 34 emails
11) 350 * 72% = 252 friends
12) 220 * 5% = 11 files
13) 4/20 = 0.20 x 100% = 20%
17) 56 ÷ 4% = 140 days
18) 60 ÷ 20% = 300 minutes
19) 32 ÷ 80% = 40 games
20) 360 ÷ 24% = 1500 kilometers
22) 9 ÷ 3% = 300 stores
24) 24/200 = 0.12 x 100% = 12%
25) 35 ÷ 7% = 500 price of the stereo
27) 1.50 ÷ 5% = 30 cost of helmet before tax
28) there are 24 hours in a day.
sleep        : 24 *  40% =  9.6 hours
school      : 24 *  25% =   6    hours
eating       : 24 * 10% =   2.4 hours
free time   : 24 * 15% =   3.6 hours
homework : 24 * 10% =   2.4 hours 

Ithink it’s b because it say 3 plastic rings and all the balls