You need to distribute the numerical factors for each term in the parenthesis:
[tex] \dfrac{-1}{5}(5x+20)-\dfrac{1}{4}(4x-28) = \dfrac{-1}{5}\cdot 5x + \dfrac{-1}{5}\cdot 20 + \dfrac{-1}{4} \cdot 4x + \dfrac{-1}{4} \cdot (-28) [/tex]
This equals
[tex] -x-4-x+7 = -2x+3 [/tex]
