9 times a number 9 is 36 an equation that represents this sentence is?

If f(x)= 3x+6 which of the following is the inverse of f(x)

Ineed ! the person who answers and shows their work on they got the answer first will be marked the !

Ametal rod needs to be 9 feet and 5.5 inches in length. the sections of the poles being used are each 1 foot and 10.5 inches long. how many 1ft 10.5in sections would be needed to complete the 9ft 5.5in metal rod? and how many inches of material will be left?