Answer:
315 (C)
Explanation:
If it takes 45 minutes to make 3 bracelets, (considering she spends equal time on each) she's making 1 bracelet every 15 minutes. There are two ways you can solve this.
45/3 = 15 times 21 (bracelets) = 315
Or,
21/3 is 7, so multiply 7 and 45 to get 315 as well.
(Second Question) If we're finding percentages you always want to find a number out of 100. We can get to 100 evenly by multiplying 25 by 4. Do the same for 15 so the ratio stays equal, and you get 60, or: 60%.