Answer:
Step-by-step explanation:
You can split the coins into 3 groups, each of them has 3 coins. Weigh group 1 vs group 2, if one is lighter, that group has the fake coin. If both groups weigh the same, then group 3 has the fake coin.
Continue to split the group that has the fake coin into 3 groups, each group has 1 coin. Now apply the same procedure and we can identify the fake coin.
Total of scale usage is 2
b) if you have 
coins then you can apply the same approach and find the fake coin with just n steps. By splitting up to 3 groups each step, after each step you should be able to narrow down your suspected coin by 3 times.
Step 1: you narrow down to group of 
coins
Step 2: you narrow down to group of 
coins
Step 3: you narrow down to group of 
coins
...
Step n: Step 1: you narrow down to group of 
coin
First, you need to get the denominators (the bottom number) the same. The smallest number to get them to is 15.
So, what you need to do is take 2/5 and multiply the bottom by 3 to get 15, and since you did it to the bottom, you need to do it to the top too. So you would get, 6/15.
Then, for 1/3, take the bottom number and multiply it by 5. Then, since you did it to the bottom, do it to the top as well. You would get 5/15.
Then, you need to put them side by side. You don't add the bottom, so your denominator would remain 15, but your numerator (top) would get added.
<u> 6</u> + <u>5</u> = <u>11</u>
15 15 15
Number 7 is C because all of them are less than 1/2 or 0.50
1) Well you divide the copies by 14 for the amount of friends that Ivan has helping him then multiply that to the 0.25 cents that he is playing them.
2) You multiply 1428 of the copies of flyers to the 0.10 then add that answer to the answer of number 1
