B. 17.16 represents a credit of $17.16; "credits" mean that you're receiving something, so it's added. A is incorrect because it shows the money being taken away and that isn't what a credit does. C and D aren't even the same amount of money in the question, so they aren't your answer either.
149 will be rounded to 150 so 150×5= 750
An estimate for the number of ducks would be 62.
There were 30 the first day.
The second day, 8 of those 30 were there as well, so we subtract that from the 40 ducks and get 32.
Add 30 and 32 to get our estimate.
