Can you help me with this?

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

Tabby sells clothing at a retail store, and she earns a commission of 6.25% on all items she sells. last week she sold a pair of jeans for $32.50, a skirt for $18.95, and 2 blouses for $14.95 each. what was tabby's total commission? a $4.15 b $5.08 c $81.35 d $348.60

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.