If the battery has a voltage of 9 v and the light bulbs have resistance of 10 ohms 20 ohms and 30 ohms What is the voltage across light bulb 2?

Assume you mean resistors in a series ckt, since in a parallel ckt the answer is 9V.

First solve for total current: I=E/Rtotal Rt=10+20+30, or 9/60, so 150ma

then for each R:

E=IR

R1=10, so 10*.15=1.5

R2=20, so 20*.15=3.0

R3=30, so 30*.15=4.5

The source 9V= the sum of the voltage drops as a sanity check.