How to find voltage across resistors with only current sources?
Here, let me set up the equations for you:







simulate this circuit &ndash; Schematic created using CircuitLab

You have five unknowns &mdash; three currents and two voltages. We'll need five equations.

KCL tells us that the sum of currents into any node must be zero:

$$I_{L1} + I1 - I_{L2} = 0$$

$$I_{L2} - I2 - I_{L3} = 0$$

$$-I_{L1} - I1 + I2 + I_{L3} = 0$$

Note that the third equation tells us nothing new; it is simply a combination of the first two.

KVL tells us that the sum of voltages around a loop must be zero, which is really just another way of saying that the voltage across I1 must equal the voltage across R1, etc. We simply apply Ohm's Law to the resistors:

$$V1 = -I_{L1} \cdot R1$$

$$V1 - V2 = I_{L2} \cdot R2$$

$$V2 = I_{L3} \cdot R3$$

Now we have five independent equations that we can solve for our five unknowns.

As Alfred Centauri says, the principle of superposition makes this problem almost trivial to solve, but you may not have been exposed to that yet.