If $\dfrac{x - 2}{4} - \dfrac{x - 3}{5} = 1$, the value of x is:

1. -42

2. 42

3. -18

4. 18

$\dfrac{x - 2}{4} - \dfrac{x - 3}{5} = 1$

Since L.C.M. of denominators 4 and 5 = 20, multiply each term by 20 to get:

⇒ $\dfrac{20(x - 2)}{4} - \dfrac{20(x - 3)}{5} = 1 \times 20$

⇒ 5(x - 2) - 4(x - 3) = 20

⇒ 5x - 10 - 4x + 12 = 20

⇒ x + 2 = 20

⇒ x = 20 - 2

⇒ x = 18

Hence, option 4 is the correct option.