Answer:

Step-by-step explanation:
Given :

Multiply numerator and denominator by 2 :

[Divide both sides by 5 as it is a common factor]

Answer:
The first one and the last one are true (Since −6 is 6 units to the left of 0, |−6|=6 and −6 is closer to zero on the number line than −7, so |−6|<|−7|.)
Step-by-step explanation:
Absolute value is the distance to zero, and it is always positive. That means the positive and negative versions of a number have the same absolute value. That means the first one is true, and the second and third ones are false. For the last one, -6 is closer to zero, so that means it would be true (The absolute value of -6 is 6, and the absolute value of -7 is 7).
Answer:
We can use the sample about 42 days.
Step-by-step explanation:
Decay Equation:



Integrating both sides


When t=0, N=
= initial amount




.......(1)
.........(2)
Logarithm:
130 days is the half-life of the given radioactive element.
For half life,
,
days.
we plug all values in equation (1)






We need to find the time when the sample remains 80% of its original.







We can use the sample about 42 days.