Answer
$\dfrac{1}{60}$
Work Step by Step
Find the LCM (lease common multiple) of the denominators:
$20 = 5(2)(2)
\\15=5(3)$
The LCM is $5(3)(2)(2) = 60$
Thus, the LCD is also $60$.
Make the fractions similar using their LCD to obtain:
$=\dfrac{3(3)}{20(3)} - \dfrac{2(4)}{15(4)}
\\=\dfrac{9}{60}-\dfrac{8}{60}
\\=\dfrac{9-8}{60}
\\=\dfrac{1}{60}$
