As x approaches 3 from the right, the limit is 3. There is a closed hole up there AT x=3 y=7, but we don't care about what happens AT x=3, only what happens as x APPROACHES 3.
The answer is D. 3 and 17.
3 + 17 = 20. They have a sum of 20.
17 - 3 = 14. They also have a difference of 14.
Hope I helped!
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