For $\dfrac{5}{x} = \dfrac{7}{x - 4}$, the value of x is:

1. -10

2. 10

3. 5

4. -5

$\dfrac{5}{x} = \dfrac{7}{x - 4}$

On cross multiplying, we get :

⇒ 5 $\times$ (x - 4) = 7 $\times$ x

⇒ 5 $\times$ x - 5 $\times$ 4 = 7x

⇒ 5x - 20 = 7x

⇒ 5x - 7x = 20

⇒ - 2x = 20

⇒ x = - $\dfrac{20}{2}$

⇒ x = - 10

Hence, option 1 is the correct option.