We are given a series circuit with two light bulbs. In this case, the light bulbs act as resistors in series and the total resistance is:
[tex]R_t=R_1+R_2[/tex]That is the sum of all the resistances in series in the circuit. To determine the voltage we can use Ohm's law:
[tex]V=IR[/tex]Where "R" is the total resistance and "I" is the current in the circuit. Replacing we get:
[tex]V=I(R_1+R_2)[/tex]