A positive number when decreased by 4 is equal to 21 times the reciprocal of the number. The number is:  Choose the correct choice from the following answers:
A) 2 B) 5 C) 9 D) 7 E) 6

Rationale: let the number be x x - 4 = 21 / x x ^ 2 - 4 x - 21 = 0 ( x - 7 ) ( x + 3 ) = 0 x = 7 correct answer d
Answer: D