12. \( \frac{4}{5}-\frac{3}{5} \cdot\left(\frac{1}{3}\right)^{-1} \)

To solve the expression \( \frac{4}{5}-\frac{3}{5} \cdot\left(\frac{1}{3}\right)^{-1} \), start by simplifying \( \left(\frac{1}{3}\right)^{-1} \). The reciprocal of \( \frac{1}{3} \) is \( 3 \). So the expression becomes: \[ \frac{4}{5} - \frac{3}{5} \cdot 3 \] Now calculate \( \frac{3}{5} \cdot 3 \): \[ \frac{3 \cdot 3}{5} = \frac{9}{5} \] Substituting that back into the expression gives: \[ \frac{4}{5} - \frac{9}{5} \] Now, combine the fractions: \[ \frac{4 - 9}{5} = \frac{-5}{5} = -1 \] Thus, the final answer is: \[ -1 \]