[tex]30 \Omega || 40\Omega ~ \text{and}~50\Omega || 30 \Omega\\\\\text{Equivalent resistance of the whole circuit,}\\ \\R_{eq} = \left(\dfrac{30 \times 40}{30+40} \right) + \left( \dfrac{50 \times 30}{50+30} \right)\\\\\\~~~~~~=\dfrac{1005}{28}~ \Omega\\\\\text{By Ohm's law,}\\\\~~~~~V=IR\\\\\implies I = \dfrac{V}{R} = \dfrac{9}{\tfrac{1005}{28}} = \dfrac{252}{1005}= \dfrac{84}{335}~ A\\\\ \text{Voltage drop between points A and B,}\\\\V_{AB} = IR_{AB}\\\\\\[/tex]
[tex]~~~~~~~=\dfrac{84}{335} \cdot \left(\dfrac{30 \times 40}{30+40} \right)\\\\\\~~~~~~~= \left( \dfrac{84}{335} \right) \left(\dfrac{120} 7 \right)\\\\\\~~~~~~~=\dfrac{288}{67}~V\\\\\\~~~~~~~=4.298~V[/tex]
