Ericas apartment house are consecutively numbered on each floor. the sum of her and her neighbors number is 2409. what are the 2 numbers?

2 apartments consecutively numbered : x and x + 1

x + (x + 1) = 2409

2x + 1 = 2409

2x = 2409 - 1

2x = 2408

x = 2408/2

x = 1204

x + 1 = 1204 + 1 = 1205

so the 2 numbers are : 1204 and 1205