58
First solve what is inside the parentheses (PEMDAS)
(5-21)+(-7+81)
(-16)+(74)
Add
58
Hope this helps! :)
Answer: the answer is 4
Step-by-step explanation:
when looking for the half life, it says to look for when the initial amount is half of what it used to be, because it is 100, 100 divided by 2 is 50, and when looking at the hours (x value) for 50 it says 4.
Answer: 11.4
Step-by-step explanation:
change to numbers 
simplify 
Answer:
5/4
Step-by-step explanation:
(y₂ - y₁) / (x₂ - x₁)
(4,9) (-8, -6)
plug in
(-6 - 9) / (-8 - 4)
solve within parentheses
-15/-12
simplify
5/4