90 students represent x percent of the boys at Jones Elementary School. If the boys at Jones Elementary make up 70% of the total school population of x students, what is x? Choose the correct choice from the following choices.
A) 113  B) 150  C) 225  D) 250  E) 500

Rationale: "90 = x / 100 * 70 / 100 * x = > x ^ 2 = 9 * 10000 / 7 = > x = 113 a"
Answer: A