1. 9y - 63 = 9 ( y - 7 )
2. 12y - 42 = 3 ( 4y - 14 )
3. 5y + 5 = 5 ( y + 1 )
4. 7y - 7z = 7 ( y - z )
5. xy + yz = y ( x + z )
6. x^2 + 3x = x ( x + 3 )
