A positive number when decreased by 4 is equal to 21 times the reciprocal of the number. The number is	Choose the correct option:	A) 3	B) 5	C) 7	D) 9	E) 12

Rationale: "sol . let the numbers be x . then , x - 4 = 21 / x ⇔ x 2 - 4 x - 21 = 0 ⇔ ( x - 7 ) ( x + 3 ) = 0 ⇔ x = 7 . answer c"
Answer: C