$a)3\left(x-y\right)=3x-3y$

$b)4\left(a+b\right)=4a+4b$

$c)-2\left(2x-y\right)=-4x+2y$

$d)-5\left(-3a+2+b\right)=15a-10-5b$

$e)4\left(-2x+y-1\right)=-8x+4y-4$

$f)-3\left(3-2xy+5y\right)=-9+6xy-15y$