Which answer matches the sentence? 9 is 3 less than a number n

1. 9=3-n
2.9=n+3
3. 9=3n
4. 9=n-3

Two cities a and b are 1400km apart and lie on the same n-s line. the latitude of city a is 23 degrees. what is the latitude of city b. the radius of the earth is approximately 6400km.