As per your x-ray both 6 and 7 have large cavities that have entered the pulp of the tooth . This is usually associated with pain on biting and or spontaneous pain during the night . Cracks cannot be diagnosed with a x-ray . Direct clinical examination would be required
Next Steps
You will need root canal treatment in both 6 and 7 , followed by crowns on both .
Health Tips
I am quite sure the dentist who took this x-ray gave you the same opinion