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.
X = 1, -5 ,,,,,,,,,,,,,,,,,,,,,,,
9/27
there are infinite ratios equal to 9/27
one if the ratio is 1/3
This is a basic addition/subtraction question. It's saying that they started at the 50 yard line. On the play, they gained 7 yards. So, we'll add 50+7 = 57.
They're at the 57 yard line at this point. On the second play they lost 10 yards (how unfortunate). Thereby, we will subtract 57-10=47.
50 yards +7 yards. -10 yards.
The answer will be that they'll be on the 47 yard line on the next play.
the perimeter is simply the sum of all its sides.
(6a+8)+(12a)+(6a+8)+(10a-4)
34a + 16 - 4
34a + 12.
