Art, Music, and Creative Writing homework help

According to the American Heart Association, 19% of U.S. adultssmoke cigarettes. If you were to randomly select 5 U.S. adults, what is the probability that 4 or 5 of them would not smoke? I know that the answer is .7576 and i used 1-binomcdf(5,.81,3) but i don’t understand why i need help explaining step by step