To find the total floor area \( n \) of all the offices in the building, you would multiply the number of offices by the floor area of each office.
The correct equation would be:
\[ 23 \times 305 = n \]
Calculating that gives:
\[ n = 23 \times 305 = 7,015 \text{ square feet} \]
So the correct choice is:
\[ 23 \times 305 = n, , n = 7,015 \text{ square feet} \]