Non zero digits are always significant. any zeros between two significant digits are significant. a final zero or trailing zero in the decimal portion only are significant.
1) not function because 6 number repeat in domain
2) Function
For 3 and 4 I guess it's
3) Function
4)not function
If any number repeat twice in the domain that will be not a function
4-x=3
Double the 3 witch is =6
And add 8 witch is
6+8=14
That means our price markup is $67.00-$50.00=$17.00