Answer : The energy released by the decay of 3 grams of 'Th' is 
Explanation :
First we have to calculate the mass defect
.
The balanced reaction is,

Mass defect = Sum of mass of product - sum of mass of reactants


conversion used : 
Now we have to calculate the energy released.



The energy released is 
Now we have to calculate the energy released by the decay of 3 grams of 'Th'.
As, 230 grams of Th release energy = 
So, 3 grams of Th release energy = 
Therefore, the energy released by the decay of 3 grams of 'Th' is 