\(6xy-12y=6y\left(x-2\right)\\ b,5x^2-5xy-3x+3y=\left(5x^2-5xy\right)-\left(3x-3y\right)=5x\left(x-y\right)-3\left(x-y\right)=\left(x-y\right)\left(5x-3\right)\\ c,x^2-2xy-36+y^2=\left(x^2-2xy+y^2\right)-36=\left(x-y\right)^2-6^2=\left(x-y-6\right)\left(x-y+6\right)\)