12-y=9
3x-y=21
4y-10=2
1/4xy=6
You and your friend made 13 each
So first you would combine the like-terms so you get:

and combine the second like-terms:

now you only have a two step equation and you continue by doing the reciprocal and you add the -1/5 to the 24.8 where you get:
7/9x=24.6
then because the 7/9 is being multiplied by the x and your trying to isolate it you divide it by the 7/9 on both sides and you'll end up getting
x=31.628571429....
The problem presented with the word used as "divied" is very tricky and misleading to the point that it might create an understanding.
So we will approach this is in two ways.
If this was meant to be "divided by" then it would look like this:
6 / 192
If this was meant to be "divided to" then it would look like this:
192 / 6
Let us first solve for the first possible problem:
6 / 192 = ?
0.0312
0.0312 would be the answer.
Let us then solve for the second possible problem:
192 / 6 = ?
32 = ?
32 would be the answer.
So 0.0312 and 32 would be two possible answers to this problem.
The difference would be 0.27