Question 112878
let x="original speed", so x+20="increased speed" ___ time=distance/rate


the plane flies 480 mi @ x; and (840-480) mi @ x+20


(480/x)+(360/(x+20))=5 ___ 480(x+20)+360(x)=5(x)(x+20) ___ 96(x+20)+72(x)=x(x+20)


0=x^2-148x-1920 ___ 0=(x+12)(x-160)