Answer:
C. 12
Step-by-step explanation:
With the rule of 72, you would divide 72 by the periodic interest rate to get the number of years for the principal to double
72 ÷ 6 = 12
If similarity ratio means the ratio between the lengths of the cubes:
Answer:
a) 
And if we solve for
we got:

b) False
The reason is because we don't satisfy the following relationship:

We have that:

c) False
In order to satisfy independence we need to have the following condition:

And for this case we don't satisfy this relation since:

Step-by-step explanation:
For this case we have the following probabilities given:

Part a
We want to calculate the following probability: 
And we can use the total probability rule given by:

And if we solve for
we got:

Part b
False
The reason is because we don't satisfy the following relationship:

We have that:

Part c
False
In order to satisfy independence we need to have the following condition:

And for this case we don't satisfy this relation since:

I don’t see the question.
Know that:
sin(β)=Opposite/Hypotenuse
Therefore:
sin(54)=x/10
Therefore:
x=10*sin(54)
x=8.1 (To the nearest tenth)