By what number should $\dfrac{12}{17}$ be multiplied to get $-\dfrac{4}{7}$?

Let the number be $x$

$\dfrac{12}{17} \times x = -\dfrac{4}{7}\\[1em] ⇒ x = -\dfrac{4}{7} ÷ \dfrac{12}{17}\\[1em] ⇒ x = -\dfrac{4}{7} \times \dfrac{17}{12}\\[1em] ⇒ x = -\dfrac{4 \times 17}{7 \times 12}\\[1em] ⇒ x = -\dfrac{68}{84}\\[1em] ⇒ x = -\dfrac{17}{21}$

$-\dfrac{17}{21}$ must be multiplied by $\dfrac{12}{17}$ so that the product is $-\dfrac{4}{7}$.