Finding Thevenin equivalent circuit

For , short circuit all independent voltage sources.

The resistances 5Ω and 15Ω can be combined in parallel as,

The network then simplifies to a form shown,         

Hence,

For

Applying KVL in upper loop,

                --------------(1)        

Applying KVL in lower loop

                --------------(2)

Solving equation 1 & 2

,        

Using KVL

So, thevenin equivalent circuit will look like as shown,

So the current through resistor ‘R’