Question

If a, b and c are positive integers such that a + b = 9 and ac − 2 bc = 0, what is the value of a?

Answer 1

ac - 2bc = 0
c(a - 2b) = 0
so a - 2b = 0............................................................(1)
    a + b   = 9    Multiply this equation by 2:-
   2a + 2b =18   .......................................................(2)
 Adding equations (1) and (2):-

 3a = 18  
  a =  6   answer