(a) According to the question, calculate current in the circuit
R1 = 6 ohm
R2 = 4 ohm
R = R1 + R2
R = 6 + 4
R = 10 ohm
V = 20 V
I = V / R
I = 20 / 10
I = 2 A
(b) To find the voltage across the resister of 6 ohm.
R = 6 ohm
I = 2 A
V =?
V = IR
V = 6 × 2
V = 12 V