Depending on which source you examine each time, you have a different configuration. Take a look here for an example: http://www.allaboutcircuits.com/vol_1/chpt_10/7.html
You do not need to know the value of R in this circuit. Since it is in parallel with a voltage source, it will not effect the value of the voltage Vx. hgmjr
To find Vx, you only need to know the current flowing through the 5Ω resistor. R doesn't matter, as the voltage across R is 10V. That value is needed for the voltage on the left side of the top resistor. Check out the links given above, giving you the answer to this question will not help you at all if the resistors change, or the current source and voltage source are switched around for the test.
ok, but What is the current passing through the resistance 5?? Current in the resistance 5 of voltage source and current source , right?? And how I find?? They gave me the solution please my exam tomorrow
The current through R WILL add to the total current being used by the circuit, but that current doesn't matter when calculating Vx (the current through the 5 Ohm). Hopefully that was explained to you in class.