What's the probability of flipping a coin 5 times and getting at least three tails?

Which shows the correct substitution of the values a,b and c from the equation 1=-2x+3x^2+1

Solve for x and y a x= 13.3 y= 16.7 b x= 23.3 y= 12.5 c x= 7.5 y= 16.7 d x=7.5 y= 12.5

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible