Interpreting your expression as

when
approaches zero, the numerator approaches 3:

The denominator approaches 0, because 
Moreover, we have

So, the limit does not exist, because left and right limits are different:

Years of decay...
It takes around 4 years for something to go through their half life (depending on the thing). This chart is showing the years go by (half lives that occur within the years) while the decaying is happening.
Answer:
x=1.6
Step-by-step explanation:
first follow PEMDAS
so you multiply -2 into the parentheses
-8x and +10
so now it is
5x+3x=-8x+10
add 5x +3x
get 8x
then we have
8x=-8x+10
add -8 to the other side
get 16x
so now 16x=10
divide 16 by 10
get x=1.6
The answer is 21.5 because 7-3 is 4 so 43 divided 4 is 10.75 so 10.75 times 2 is 21.5