Two numbers N and 12 have LCM = 42 and GCF = 6. Find N.  Choose the correct option
A) 35  B) 56  C) 21  D) 87  E) 24

Rationale: "the product of two integers is equal to the product of their lcm and gcf . hence . 12 * n = 42 * 6 n = 42 * 6 / 12 = 21 correct answer c"
Answer: C