Express $\dfrac{-48}{60}$ as a rational number with denominator 25.

First reduce the given rational number to its lowest terms, then multiply both the numerator and the denominator by the same number to get the denominator 25.

HCF of 48 and 60 = 12.

$\Rightarrow \dfrac{-48}{60} = \dfrac{-48 \div 12}{60 \div 12} = \dfrac{-4}{5} \\[1em] [5 \times 5 = 25] \\[1em] \Rightarrow \dfrac{-4}{5} = \dfrac{-4 \times 5}{5 \times 5} \\[1em] \Rightarrow \dfrac{-20}{25}$

Hence, $\mathbf{\dfrac{-48}{60} = \dfrac{-20}{25}}$.