[tex]\mathfrak{\huge{\orange{\underline{\underline{AnSwEr:-}}}}}[/tex]
Actually Welcome to the Concept of the Current Electricity.
Since here, A potential divider is setup with two resisters in series, that is 3 ohm and 6 ohm.
As the voltage is always in directly proportional to the resistance,by ohm law,
V = IR, so the increase in Voltage will lead to increase in the resistance too.
hence,
for 6 ohm the voltage is 4 V, then for the 3 ohm it would be ,
V1 = (4/6)*3
==> V1 = 2 Volts,
==> hence the potential V1 = 2V
