Question

The apartments in Brian's apartment house are numbered consecutively on each floor. The sum of his number and his next-door neighbor's number is 1419. What are the two numbers?

Answer 1

If sum of numbers (a) +(b) is 1419 and
(a)  and (b) are neighbors , whe have:
a + b = 1419 and b-a = 1;
<=> a + b = 1419  and  a = b-1 ; 
so we have  b-1 + b = 1419 <=> 2b = 1420 <=> b=710 and a = 709
Answer: 710 and 709

Answer 2

You should the number they give you 1419 and divide that by two since there is only to people and you get your answer 709.5