Hi sana.noor,

For this type of question, you can draw pictures and/or do math. Your goal is to find a way to make the minimum number occur...

Let's TEST VALUES.

If there are 100 people, then we have
70 who like apples
75 who like bananas
80 who like cherries

Clearly, some people have been counted in more than 1 category. Here's how to figure out the minimum number who like all 3....

There are 80 who like cherries; that means there are 20 who DON'T.
Of the 75 who like bananas, we can say that 20 DON'T like cherries (this helps to minimize the number who like cherries AND bananas).
Now we have:
55 who like cherries AND bananas
25 who like just cherries
20 who like just bananas

Next, we factor in the apples. Of those 70 people, we can spread them around and maximize the number who like apples AND cherries OR apples and bananas, BUT NOT ALL 3.
So, let's split the 70 into:
25 who like apples and cherries
20 who like apples and bananas

That leave's 25 who MUST like cherries, bananas AND apples.

Final Answer: [spoiler]25/100 = 25% = C[/spoiler]

GMAT assassins aren't born, they're made,
Rich