B) thousands
5 is ones
7 is tens
7 is hundreds
9 is thousands
1 is ten thousands
2 is hundred thousands.
Answer: 
Step-by-step explanation:
Given
Population of dust particle doubles every 30 minutes
If the initial sample is 21 grams
The model to predict the population will be

Where t=time in hours
A day has 24 hours . So, for 2 days time is 48 hours
Population is given by
100 + x-4 +3x =180
x = 21
hope it help
Answer:
in this case it is just multiplying the two items together
the THIRD CHOICE...
3x(x^2-5x-9)
3x^3 -15x^2 -27x
Step-by-step explanation:
A = b is given to us
Multiply both sides by c to get
a = b
a*c = b*c
The rule to multiply both sides by c is the multiplicative property of equality
Then on the right side, replace c with d. This replacement is possible due to the fact that c = d. This is using the substitution property.
So we go from
a*c = b*c
to this
a*c = b*d