the bill you pay is $720 a year.if you pay it monthly, you will pay $70/month. thats a monthly $840 each year. How much would you need to save each month?

Umh, if you are going to pay $70 per month, wouldn't you want to save $70 each month so you can pay it?

I really don't understand your question, what am I missing?
Check the wording, "you will pay $70/month. thats a monthly $840 each year" makes no sense.