For this case the first thing you should know is that we have the following definition:
V = I * R
Where,
V: voltage
I: current
R: resistance
Therefore, by clearing the Resistance we have:
R = V / I
Substituting the values:
R = 12/48
R = 1/4 ohms
Answer:
The value of the resistance is:
R = 1/4 ohms