the chart in GSH states that a flush draw breaks even at 4.1-to-1, yet when dividing 9 into 47 i get 5.2 which would make it 5.2-to-1 (i assume this is how to calculate the odds). TOP states that drawing to a flush makes you a 5-to-1 underdog. im terrible at math and such but there seems to be a discrepancy. if there is, why?

also, can somebody tell me how, or if it's too complicated, can somebody direct me to a source to learn how to calculate the odds of anything happening in Hold em?