If 80% of 90 is greater than 70% of a number by 30, what is the number?  Choose the correct choice: A) 70 B) 60 C) 10 D) 75 E) 85

Rationale: "explanation : 80 / 100 * 90 - 70 / 100 * x = 30 72 - 70 / 100 * x = 30 72 - 30 = 70 / 100 * x 42 = 70 / 100 * x 42 * 100 / 70 = x 60 = x answer : option b"
Answer: B