**options**

A) 42.5 Days

B) 40 Days

C) 36.5 Days

D) 37.5 Days

*Detailed solution *

Lets take it as 100, then

X = 150

Y = 100

X/Y = 150/100 = 3/2

Efficiency of work are in above ratio.

( Efficiency is always inversely proportion to time)

Total work = 15 days ( 2+3) unit

= 75 unit

Complete work

75/2 = 37.5

Answer 37.5