Answer:
4.88g
Step-by-step explanation:
We must first calculate how many half-life there are in 18 hours, knowing that each half life takes 2 hours.
18/2 = 9 Half life
Now, knowing this we can calculate the number of grams by applying 9 times the half life.
2500/2= 4.88 grams
Which means that after 18 hours there are 4.88 grams.