I have a cast iron toilet drain that is cracked at the flang down the side. It goes streight down into a 90 degree pipe with a concetion that goes to the roof for air flow. How do I replace this cast iron with pvc? Thank you

You cut the cast iron pipe so some of the pipe sticks out at least 6 inches. Then using a No-Hub Band, (see image) you couple on a piece of PVC, prime and glue on a elbo and stub up for your closet flange. Good luck, Tom