Question

3x + y = 6
x - y = 6

Answer 1

x = 3
y = -3

Answer 2

Because when you take negatives away from positives then you're adding more negatives.

Answer 3

So if x were 3 the for the first question:
3x + y = 6
3 ( x = 3) so 3x3=9
Then it would become:
9 + y = 6
So to add anything to make it a smaller number ( for positives ) then the number would have to be a negative. 9 + -? = 6.
-? = -3 because 9 + -3 = 6.

x - y = 6

x=3
y+-3

x(3)-y(-3)=6

( You would know if you read my comment on negative )

"Because when you take negatives away from positives then you're adding more negatives."