A box contains 6 cards numbered 1-7 one card is selected at random and replaced what is the probability that you can select a 4 and then a prime number

Bring the fraction a/a-4 to a denominator of 16-a^2

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

If you have 12 feet of string and you cut it into equal length of 5 inches each how much string will be left