Multiplying and dividing rational numbers

$\dfrac a b \div \dfrac c d = \dfrac a b \times \dfrac d c$

$-1 ~\dfrac 7 8 =-\dfrac{15}{8} \\ -\dfrac{15}{8} \div \dfrac 3 4 = -\dfrac{15}{8} \times \dfrac 4 3 = -\dfrac{60}{24} = -\dfrac{5}{2}$