I encourage you to utilize the reference problems that you have been given already to tackle this problem. Below is the link to those reference problems:
1. https://web2.0calc.com/questions/3x-6y-x-3-y-6
2. https://web2.0calc.com/questions/please-answer-asap_5
3. https://web2.0calc.com/questions/please-answer-asap-please
These are just a few reference problems that you can use!
Upon further review, it appears as if the answer I provided for the second question got flagged for something. Luckily for you, though, you have a myriad of problems to refer to anyway.