60 there refers to only mac, so you shouldn't be subtracting 20 there.
number of people who preferred mac to windows ( in other words they only prefer mac ) = mac only = 60
1/3 as many who preferred mac to windows , preferred both equally = mac & windows = (1/3)*60 = 20
let number of people who prefer windows to mac = windows only = x
also given number of people who prefer nothing = 90
=> total = mac only + windows only + mac & windows + neither
210 = 60 + x + 20 + 90
=> x = 40
Answer is B.
Thanks for the reply.
I was bit confused with this question during the exam. Does the "60" refer Only Mac or both Windows and Mac?.
I messed it up during the exam as given below:
Can you please help me in pointing out what went wrong?