I´m an electrical engineering student taking my first circuits subject!! I´m super hyped but kinda stucked at this problem.

By KVL on left side i got that I_1 = 10 A , and by the right side i get to V_3+Vi=12V

and using KCL that I_2+I_3= 15 A

Since yesterday i got stucked on this, tried to use R3*(15-I2)+Vi=12 but yet still unconclusive.

I feel like i`m running in circles with this problem, always finding new equations although they are linear dependent

Answer is 0.8 Ω btw