Question 760707
   a + 6b =  2      .....(1)
   a - 3b = -1 
(-) (+)   (+)
_____________
   0 + 9b = 3
        b = 3/9
        b = 1/3       ....(2)
  Putting (2) in (1) we get

  a + 6(1/3) = 2
  a + 2 = 2
  a = 0
 
Therefore a = 0   and   b = 1/3