Answer: 49 people
Step-by-step explanation:
First you need to separate the people that read both from the people that read the daily news. Do this by subtracting 171 - 40 = 131.
Now you can subtract the total amount of people that only read the Daily Mews from the total amount of people polled (198-131=67)
From here you need to subtract the amount of people that read neither from the remaining total. (67-18=49)
this is where you get the 49 people out of 198 that read the Sun Gazette