All these resistors are in series so we can take the sum of them by:
Rtotal = R1 + R2 + R3......
So...
Rtotal = 2 + 3 + 4 + 6
Rtotal = 15
So now the total resistance in the circuit is 15 ohms and the potential difference applied to the circuit is 45 volts
Now we can use:
V = IR
Isolate for I
V/R = I
45/15 = I
I = 3 amps (A)
