#### Answer

$f^{-1}(x) = \frac{x+7}{1.4}$

#### Work Step by Step

$f(x) = 1.4x - 7$
Let $f(x) = y$
$y = 1.4x - 7$
Swap the variables $x$ and $y$ and then solve for $y$ to find the inverse:
$x = 1.4y - 7$
$x + 7 = 1.4y$
$y = \frac{x+7}{1.4}$
$f^{-1}(x) = \frac{x+7}{1.4}$