Finding voltage thevenin
Convert current sources to voltage sources and we'll get a simpler circuit.







simulate this circuit &ndash; Schematic created using CircuitLab

Using nodal law at A,

$$\frac{V_A}{18} + \frac{(V_A-16)}{22} + \frac{(V_A-199)}{14} = 0$$

On solving, we will get \$V_A = 86.65 V\$

So the current through R1 and R9: 
$$I = (V_A - 199)/14 = -8.025 A$$

Note the minus sign. The direction of I is therefore from ground to the node A, through R9 and R1.

let us find \$V_B\$:
$$V_B = 144  - IR_9 = 144 - 48.15 = 95.85 V$$

Therefore the thevenins voltage \$V_{AB} \$ will be:
$$ V_{AB} = V_A - V_B = -9.2V$$