a certain airline ' s fleet consisted of 110 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 ?
let x be the number of years . 4 x > 110 - 3 x 7 x > 110 x > 15 + 5 / 7 the answer is b .
divide(110, add(const_3, const_4))