A No-Brainer

Example 1:

Bill: Do you have plans for vacation, Mike?
Mike: Nope. I can't decide what I want to do. My roommates want to go to Las Vegas, but my parents want to take me on a cruise through Mexico.
Bill: Mike! That's a no-brainer! You can go to Vegas anytime! The cruise to Mexico is something you shouldn't pass up.

Example 2: 

Seth: Have you heard back from the company you interviewed with last week? I know you've been looking for work for a few months.
Ruth: Yes, actually. They called me the other day to offer me a position.
Seth: Wow! That's great! You're going to take the job, right?
Ruth: Of course! It's a no-brainer!

Explanation:
A no -brainer is an extremely easy question or decision to make.
In Example 1, Mike has to decide between a trip to Las Vegas with his friends or a cruise to Mexico with his parents. While both trips sound fun, Bill thinks the choice is obvious and easy to decide- of course he should go to Mexico! Living in southern California, Mike has plenty of opportunities to travel to Las Vegas, but it's unlikely his parents will take this same cruise again.
In Example 2, Ruth says she will take the job. To her, there is no other option. It is the obvious choice.
You can think of something as a no-brainer if someone who has no-brain can still make the decision easily.

http://languagesystems.edu/

To Take Something With a Pinch/Grain Of Salt (used as a verb)

First Example:

Lucy: Did you go to that political rally last night?
Jason: Yeah, and it was amazing! She had such great ideas, and her campaign promises are really inspiring.
Lucy: Maybe, but make sure you take anything she says with a pinch of salt.
Jason: What do you mean?
Lucy: Well, she's a politician. They're known for promising things they can't actually deliver just to get more people to vote for them.
Jason: I know, but I think she's for real.

Meaning: 

To "take (something someone says) with a pinch of salt " is a phrase that means you should be critical of what a person says. This idiom is often used when the person who says it doesn't trust something another person said, or thinks they have an ulterior motive.  In the example, Jason is excited by a political candidate, but Lucy says he should take what she says with a pinch of salt, suggesting that the candidate may be promising things she doesn't intend to deliver on.  
In addition, the word "grain" is sometimes used instead of "pinch." The idiom means the same thing with either "pinch" or "grain."

Here is another example:  
            
Bill: Want to try that restaurant that just opened?
Kelsey: I don't know; I heard their service isn't very good.              
Bill: Where did you hear that?
Kelsey: I read a review on Yelp.
Bill: Oh. Well, I take reviews on there with a grain of salt. A lot of people only write reviews if something went wrong and they want to complain.
Kelsey: True, and it got a pretty good review in the paper. Yeah, let's try it and decide for ourselves.


In this case, Bill says to take online reviews with a grain of salt, suggesting online reviews are often skewed. 

http://languagesystems.edu/