Question

3x + 3y = –9
3x – 3y = 21

Answer 1

so solving by addition !

6x= 12
x= 2

and y = -5

Answer 2

3x+3y=-9
Add -3y to both sides.3x+3y+−3y=−9+−3y3x=−3y−9
you can divide
3x/3= -3y-9/3
 x= -y-3

3x-3y=21
x=y+7