3•(3a+7c

It looks like you have an expression that you want to simplify or work with: \( 3 \cdot (3a + 7c) \).

To simplify this expression, you can distribute the \( 3 \) to both terms inside the parentheses:

\[ 3 \cdot (3a + 7c) = 3 \cdot 3a + 3 \cdot 7c \]

Calculating each term, you get:

\[ 9a + 21c \]

So, the simplified expression is:

\[ 9a + 21c \]

If you need any further assistance with this or any other topic, feel free to ask!