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(i) 12x + 15

Taking 3 as common from the whole, we get,

12x + 15 = 3(4x + 5).

(ii) 14m – 21,

Taking 7 as common from the whole, we get,

14m – 21 = 7(2m – 3)

(iii) 9n – 12n²,

Taking 3n as common from the whole, we get,

9n – 12n² = 3n (3 – 4n).