#### Answer

$\frac{dy}{dx} = -7e^{5-7x}$

#### Work Step by Step

$y = e^{u}$
where,
$u = 5-7x$
Now,
$\frac{dy}{du} = e^{u} $
and,
$\frac{du}{dx} = -7$
So,
$\frac{dy}{dx} = \frac{dy}{du} \times \frac{du}{dx}$
$\frac{dy}{dx} = -7 \times e^{u}$
$\frac{dy}{dx} = -7e^{5-7x}$