Answer : It will take 3 days for one half of a 10g sample to decay.
Explanation :
Half-life period : It is defined as the time taken for half life of the reaction to complete that is the time in which the concentration of a reactant is reduced to half of its original value.
As per given in the question,
The half-life of isotope X = 3 days
when the original amount of sample (10g) will be half then the half-life of sample is, 3 days.
Hence, it will take 3 days for one half of a 10g sample to decay.