What is the inverse of y=•5x+4

First, get x by itself

y = 5x + 4    subtract 4 from both sides

y - 4 = 5x     divide both sides by 5

(y - 4) / 5 = x     "switch"  x and y

(x - 4) / 5 = y      for 'y," write  f^-1(x)

So

f^-1(x)= (x - 4) / 5

And that's the inverse