Ariri, this is the solution to the problem:
Let's recall that one of the properties of exponents is the Quotient of Powers, that tells us the following:
[tex]\frac{a^x}{a^y}=a^{x\text{ - y}},\text{ when a }\ne\text{ 0}[/tex]
In consequence,
n^10/n^12 = n^10 - 12 = n ^-2
Now, we replace this way using another of the properties of the exponents, Power of Powers :
(n^x)^1 = n ^-2
n^x = n^-2
The bases are equal, we can solve this way:
x = - 2
The correct answer is
