(i) 2x = 2 × x

3x^{2} = 3 × x × x

4 = 2 × 2

The common factor is 1.

(ii) 6abc = 2 × 3 × a × b × c

24ab^{2} = 2 × 2 × 2 × 3 × a × b × b

12a^{2}b = 2 × 2 × 3 × a × a × b

The common factors are 2, 3, a, b.

And, 2 × 3 × a × b = 6ab

(iii) 16x^{3} = 2 × 2 × 2 × 2 × x × x × x −4x^{2} = −1 × 2 × 2 × x × x

32x = 2 × 2 × 2 × 2 × 2 × x

The common factors are 2, 2, x.

And, 2 × 2 × x = 4x