The answer would be 16. She gave Erin 6 and kept two. That would be 8 oranges between the two of them and David got half, making the total 16 oranges.
Sure, each of the following lines.
8x-6+3x-1
11x-6-1
and, 11x-7
The plane would travel 2550 miles
By the fundamental theorem of algebra, we can write
Expanding the right hand side, we get
We want 
to be an integer, which means 
must also be integers. This means must be factors of 10. There are several possibilities:
So there are 4 possible values for : -11, -7, 7, and 11.
