License plate in a particular state display 3 letters followed by 3 numbers how many different licenses plates can be for this state

Solve: 3x+y=6 4x-2y=18 show all work !

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

Which expression gives the exact value of x?