Here is the question, for reference: I have two equations but am having trouble solving them for V, clearly by eliminating I E-(I*r)-(I*R_V)=0 V_ab=E-(I*R) Any help would be appreciated, thanks.

Nevermind, I got it, but the next problem is giving me a bit of trouble: If E = 7.5 volts and r = .45 ohms, find the minimum value of the voltmeter resistance R_V for which the voltmeter reading is within 1.0% of the emf of the battery. I am given the following equation to work with: E(1-(r/(r+R_V))