Whenever you are given a negative exponent, the value is flipped into it's reciporical. In this case, it is flipped back to 2.
+118723 Maybe this might help you accept it
$$\\5^3 \div 5^4= 5^{3-4}=5^{-1}\\\\
BUT\\\\5^3 \div 5^4= \frac{5*5*5}{5*5*5*5}=\frac{\not{5}\not{5}\not{5}}{\not{5}*\not{5}*\not{5}*5}=\frac{1}{5}\\\\
so\\\\
5^{-1}=\frac{1}{5}\\$$
By the same logic
$$2^{-1}=\frac{1}{2}$$
