Step 1:

Find the thevinins equivalent voltage.

1.Open the load resistor.

2.Calculate the Open Circuit Voltage. This is the Thevenin Voltage (V_TH).

Redraw the circuit :

The netwrok has two independent loops.

Find the current in each loop.

Loop 1:

.

Voltage at node A  :

.

Step 2:

Loop 3:

.

Voltage at node B  :

.

Step 3:

Voltage across nodes A and B is .

.

Find Thevenin Voltage .

Thevenin Voltage .

.

Therefore Thevenin Voltage .

Solution :

Thevenin Voltage is .