2x+y=6 and x+y=5
1. Subtract
2x+y=6
- x+y=5
________
2. Multiply the equation (x+y=5) by -1
* disregard the minus sign, it has nothing to do with the -1
2x+y=6
- -1(x+y=5)
________
3. Distribute
2x+y=6
- -x-y=-5
________
4. Subtract
2x+y=6
- -x-y=-5
________
x=1