Hi, how do I extract the third field of the first line?

I know how to get the first line or the third field of a file, but I can't get the single entry.

awk 'NR==1' file.txt

awk '{print $3}' file.txt

Please tell me how to combine these.

And how do I set this value into a variable?

var='awk "NR==1" file.txt'
?

But now I have to "eval" this $var, right?

I want to use $var in another expression.

Thanks for your help.