Resistor circuit problem
This is an easy question if you have a solid knowledge in basics of circuits 

So These are  steps that  I will use to solve your problem,


First find the equivalent resistance between L and M.And before that you want to ground a particular point of a circuit(this is a must because we want to find the voltage, simply we use that grounded point as the reference point. Which means we find voltage of other places with respect to that voltage. Usually we ground the negative terminal of the battery )

To find the total equivalent resistance through LM , it is better to isolate those parallel resistance. Because then we can get a clear view of it
resistance   as shown below.




So the total resistance between Land M is  




Redraw the circuit with this modification as shown below,




Now you have a simple series circuit. So for this you can use voltage divider theorem

Then you can find the potential drop through the resistor of 0.4 kiloohms resistor as ,



So this  much of voltage drop can be seen  in R1 also as it is parallel with the equivalent resistance that I found above.

Then the voltage drop through R1 is 1V