To find the total mass of the boxes of cereal, you can use the equation:
\[ 28 \times 375 = m \]
Now, let's calculate the total mass, \( m \):
\[ m = 28 \times 375 \]
Let's do the multiplication:
\[ 28 \times 375 = 10,500 \text{ grams} \]
So, the correct equation is \( 28 \times 375 = m \) and the total mass, \( m \), is 10,500 grams.
The correct option is: 28 x 375 = m; m = 10,500 grams.