(a) Current does not obey the laws of vector addition (e.g. currents meeting at a junction simply add algebraically, per Kirchhoff's current law, not via the parallelogram/vector law like true vector quantities such as force or velocity). The arrow used to represent current only indicates the assumed/conventional SENSE of flow along a specified conductor, not a direction in the sense of a vector — hence current is treated as a scalar quantity (with sign, not direction).

(b) Kirchhoff's rules method: apply the junction rule (algebraic sum of currents at a node = 0) and the loop rule (algebraic sum of potential drops and emfs around any closed loop = 0) to set up simultaneous equations for the branch currents, then solve for the current through the 3Ω resistor. (The exact resistor/emf values and circuit topology were not fully legible in the extracted question — apply the method to the actual figure.)