Answer: OPTION D.
Step-by-step explanation:
The formula for calculate the circumference of a circle is:

Where <em>r</em> is the radius.
The formula for calculate the area of a circle is:

Where <em>r</em> is the radius.
Solve for <em>r</em> from
to calculate it:

Subsitute the radius into
. Then:

Answer:
No solution
Step-by-step explanation:
21−7x=−7x−21−4
21−7x=−7x−25
21=−25
No solution
Answer: 9
Step-by-step explanation:
To square a number, you multiply it by itself twice.
In this case, your answer would be 3 x 3 = 9.
Hope it helps! :)
Second one is correct, that is an identity.
Third one is a contradiction:
6x - 15 = 3 * (2x - 6) ------> 6x - 15 = 6x - 18
Fourth one:
5x - 3 * (x - 4) = 2 * (x - 6) ---> 5x - 3x + 12 = 2x - 12 ---> 2x + 12 = 2x -12
So this is a contradiction as well.