- - Let's solve for C.
Starting off with our equation:

Transform:

Solve for that:

Solve for that for the last time and your answer is
If you're referring to the different sets of real numbers, it's the ones that you could try to do subtraction and not get an answer that still in that set.
For example, natural numbers (aka 1, 2, 3, 4, ...) are not, because 7 - 11 = -4 and -4 is not a natural number.
Also, whole numbers (aka 0, 1, 2, 3, 4, ...) has the same issue.
Basically any set of real numbers that doesn't include negative numbers will have this issue.
Interesting, have you tried Wikipedia?
8600 because 6 is more near to zero than 8.So all the numbers after 6 become 00
<span>B=89 lbs ANSWER: The mix contained 89 pounds of Type B coffee.
CHECK:
167lbs-89lbs=78 lbs She used 78 pounds of Type A coffee.
$4.35A+$5.70B=$846.60
$4.35(78)+$5.70(89)=$846.60
$339.30+$507.30=$846.60
$846.60=$846.60</span>