Simplify.

a) [[$ \displaystyle\frac {5x} {-2x} = $]]

b) [[$ \displaystyle\frac {-3x} {-3y} = $]]

c) [[$ \displaystyle\frac {6y} {-2y} = $]]

d) [[$ \displaystyle\frac {-4xy} {-y} = $]]