To simplify the expression \( 3(2 + 7x) \), you can use the distributive property.
Here’s how it works:
\[ 3(2 + 7x) = 3 \cdot 2 + 3 \cdot 7x \]
Calculating each term:
\[ 3 \cdot 2 = 6 \]
\[ 3 \cdot 7x = 21x \]
Now, combine the results:
\[ 6 + 21x \]
So, the simplified expression is:
\[ \boxed{6 + 21x} \]