Network Analysis (electrical circuits) Exercises

Hi, Could you help me how can I resolve this exercises. I'm not really good in this subject , but I'll hope you can explain me, I only want your help please .

https://k42.kn3.net/C13A22CC3.jpg

Could you please post your attempts so far, and an explanation of where you need specific help? In general, the people here do not do your homework for you--they only point you in the right direction and guide you along the way if you have specific problems.

Regards,
Matt