A resistor dissipates 2.00 W when the rms voltage of the emf is 15.0 V. At what rms voltage will the resistor dissipate 14.0 W?

Could someone . i have tried to solve myself but my calculation is off

Sally turns on her cellular telephone to speak to her friend who is located thousands of miles away. which of the following best describes how such a telephone is able to transmit and receive information? a. the cellular telephone transmits, receives, and encodes information using only sound waves. b. the cellular telephone transmits, receives, and encodes information using only electromagnetic waves. c. the cellular telephone transmits information by electromagnetic waves to a receiver which then encodes them and produces sound. d. the cellular telephone transmits information by sound waves to a receiver which then encodes them and produces electromagnetic waves.

Do you think you could give me the answers to #29?