The rms value of a sine wave whose average value equals 7.644 V is:

Concept:

RMS value of a sine wave given by;

V_RMS = V_max/√2

where;

VRMS→ RMS voltage

Vmax/√2→ Peak voltage

The average value of the sine wave is given by;

V_avg = 2V_max/π

Where;

Vavg → Average value 

Calculation:

Given;

V_avg= 7.644 V

Then;

Vavg = 2Vmax/π

V_max = 12 V

And 

VRMS = Vmax/√2 = 12/√2 = 8.484 V

Mistake Points Untill and unless zero is mentioned in the options go with the options having average value,

 Avg= (2 × max quanity) / π  otherwise take zero.