X can finish a work in 20 days. Y can finish the same work in 15 days. Yworked for 9 days and left the job. how many days does X alone need to finish the remaining work?  Choose one:
A) 3 B) 5 C) 6 D) 8 E) 9
Work done by X in 1 day = 1/20   Work done by Y in 1 day = 1/15   Work done by Y in 9 days = 9/15 = 3/5   Remaining work = 1 – 3/5 = 2/5   Number of days in which X can finish the remaining work = (2/5) / (1/20)= 
<gadget id="calculator">(2/5) / (1/20)</gadget>
<output>8</output>
8   8
<result>D</result>
X can finish a work in 20 days. Y can finish the same work in 15 days. Yworked for 9 days and left the job. how many days does X alone need to finish the remaining work?