Exponential decay formula is:
Total = start value x(1- rate) ^ time
Using the values given you get:
Total = 2(1-0.02)^t
Simplified :
Total = 2(0.98)^t
Now replace t with 10 and solve for total:
Total = 2(0.98)^10
Total = 1.634 grams left after 10 days. Round answer as needed.