There are 4 students with braces for every 7 students without braces. There are 28 sixth-grade students that have braces at Valley Middle School. How many students are in sixth grade in all?

Which answer choice listed below is thewhich answer choice listed below is the inverse function of ƒ(x) = x-3 x+3 , x ≠ -3? a) ƒ-1(x) = 3 ( x+1 x-1 ), x ≠ 1 b) ƒ-1(x) = -3 ( x+1 x-1 ), x ≠ 1 c) ƒ-1(x) = 3 ( x-1 x+1 ), x ≠ -1 d) ƒ-1(x) = -3 ( x-1 x+1 ), x ≠ -1inverse function of ƒ(x) = x-3 x+3 , x ≠ -3?