Is anyone good at chemistry if so Is it possible could someone help me please
NO LINKS I REPEAT NO LINKS

344.0 / 68.8 = 5 (no.of half life that have elapsed)
Mass remains = (1/2)^n × (original mass)
= (1/2)^5 × 200
= (0.5) ^5 × 200
= 0.03125 × 200
= 6.25 grams