Answer:
208 grams
Explanation:
Half life is the time it takes for a sample to reduce to half it's initial concentration.
In this question, 3 half lives go by. This is given as;
Let original mass be represented by x
First Half life;
Starting mass = X
Remaining mass = X/2
Second Half life;
Starting mass = X/2
Remaining mass = (X/2) / 2 = x/4
Third Half life;
Starting mass = X/4
Remaining mass = (X/4) / 2 = X/8
Since 26g was left, it means;
X/8 = 26
X = 26 * 8 = 208 grams
