Question 22195
I'm going to assume your problem is as follows:
    y = (2/7)x + 3

To form the inverse of this function:
1. Interchange "x" and "y" as follows
     x = (2/7)y + 3

2. Now solve this equation for "y" as follows

     Subtract "3" from both sides of the equation to get
    x - 3 = (2/7)y

     Multiply both sides by (7/2) to get

    (7/2)(x-3) = y

     Rewrite as follows

    y = (7/2)(x-3)

     Rewrite again as follows

    y = (7/2)x - (21/3)

This is the inverse in the form y=mx+b

Good luck
 Cheers,
Stan H.