The whole number portion is always the number to the left of the decimal. In this case it is 5. You have to be careful what you say if you are working in scientific notation.
For your second question 0.261 is the decimal portion. If the only part present was 0.261, then 0 is the whole number portion, believe it or not. Nice question. You can learn a lot from it.
Circumference of Circle A is is 42pi.
It is the same for all circles. To find the circumference, one must use the constant equation of 2pir. This equation stays the same, no matter what.
ANSWER

EXPLANATION
The given formula is

We want to solve for T in the given formula.
We multiply through by 3 first to get,

We simplify to get,

We now divide both sides by S to get,

We simplify to obtain:

or

1.

2.

3.

4.

1. Start
2. Multiply both sides by 3
3. Subtract a from both sides
4. Subtract c from each sides
Answer:

Step-by-step explanation:
Solve for y in the first equation.
, replace y with 
Solve for in the first equation.

<em>good luck, hope this helps :)</em>