The question wants us to find the thevenin's equivalent of this circuit. Vth is across R. The 5ohms and 6A was transformed into a series voltage and resistance.
The answer shows that the first loop is : -20 + 3i + Vth + 5i -30 = 0
The Above Loop is 2i - 10 - Vth = 0
My question is why does both mesh share the same current i, shouldn't they have their own respective currents i1 and i2 . Eg, -20 + 3i1 + Vth + 5i1 -30 = 0 and 2i2 - 10 - Vth = 0