Convert the voltage sources to combined current source. Find the current coming into the terminals of the load resistor from the source using V/R. That current is given as the source to the load. Two equivalent current sources in parallel with their respective resistors. In the final circuit the two current souces are added and connected in parallel with the combined resistance of the two resistors in parallel. Note that the current and voltage values for all the three circuits are sameshowing that they are equivalent.