Answer:
y = -x - 2
Step-by-step explanation:
y = mx + c
m = (-1-3)/(-1-(-5)) = -4/4 = -1
y = -x + c
(-1,-1)
-1 = -(-1) + c
c = -2
y = -x - 2
120 grams half life at 45 days would be 60 then half life of 60 in another 45 days (90 total) should be 30 grams
The answer to your question is 3