Answer:
1) 62.5
2) 50
3) 75
4) 100
Step-by-step explanation:
1)
Because it has a half-life of 25 days, half of it will decay after 25 days.
After
days, there will be
of it left.
So,
.
2)
Because it has a half-life of 25 days, half of it will decay after 25 days.
After
days, there will be
of it left.
So, 
3)
Because it has a half-life of 25 days, half of it will decay after 25 days.
After
days, there will be
of it left.
So,
.
4)
The only answer left is
grams. You can solve it the same way you solved the previous steps.