4(21•8)

To calculate \( 4(21 \cdot 8) \), first, we multiply \( 21 \) and \( 8 \):

\[ 21 \cdot 8 = 168 \]

Now, multiply \( 168 \) by \( 4 \):

\[ 4 \cdot 168 = 672 \]

So, \( 4(21 \cdot 8) = 672 \).