A certain airline's fleet consisted of 90 type A planes at the beginning of 1980. At the end of each year, starting with 1980, the airline retired 3 of the TYPE A planes and acquired 4 new type B plans. How many years did it take before the number of type A planes left in the airline's fleet was less than 50 percent of the fleet?	Select the correct option
A) 11	B) 12	C) 13	D) 14	E) 15

Rationale: "let x be the number of years . 4 x > 90 - 3 x 7 x > 90 x > 12 + 6 / 7 the answer is c ."
Answer: C