The required answer is
.
<u>what is a power rule for exponents ?</u>
is known as the power rule for exponents. Exponent times power is how you raise a number with an exponent to a power.
A number's exponent demonstrates how many times we are multiplying a given number by itself. 3^4, for instance, indicates that we are multiplying 3 by four. 3*3*3*3 is its expanded form. The power of a number is another name for an exponent. It could be an integer, a fraction, a negative integer, or a decimal.

Here, we have used the rule 
To learn more about the power rule for exponents from the given link
brainly.com/question/819893
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I don't see the picture what is it about?
Answer:
A(r)=15-3r
Step-by-step explanation:
switch the sign of +3r to make it -3r
X=-8 is the answer so it would be C