Find the value of $(-2{)}^{-1}$.

Find the value of $(-3{)}^{-1}$.

Find the value of $(-4{)}^{-1}$.

Find the value of ${\left(-\frac{1}{2}\right)}^{-1}$.

Find the value of $7^0+8^0+9^0$.

Find the value of $\left({20}^0-{23}^0\right)\times {18}^0$.

Find the value of $3^0\times 3^{-1}$.

Find the value of $2^{-1}\times 2^{-3}$.

Find the value of ${\left(3^{-1}÷4^{-1}\right)}^2$. (Give answer as improper fraction)