Answer:15 grams
Explanation: Radioactive decay is a first order reaction.
During one half life the mass of the element is reduced to half of the initial amount.
Initial amount = 120 g
Time of half-life= 2 days
Given amount of days= 6 days
Total number of half-lifes (n) = 6/2 = 3
Final amount= Initial amount/(2^n) = 120/8 = 15 g