Question

there was a surplus of office space in a city, with 400,000 square feet, or 16% of the total office space, vacant. How much office space did the city have?

Answer 1

I'd say that the total office space was 2,500,000 sq. ft,

16            400,000
-----  =      -----------
100              x

16x = 40,000,000
    x = 2,500,000