I'm not sure if this is right.
Resistance=12 ohms
Time=1 minute = 60 seconds
Power=3W
E=PT
E=3×60=180J
P=I^2R
180=I^2×12
180/12=15
I^2=15
I=✓15
But as it's in parallel, the current is shared equally between the two lamps so ✓15 is the current through one lamp. So 2✓15 = total current i.e current through the cell.
So,
Q=IT
Q=2✓15×60
Q=465 C (to 3 s.f)