Finding the values of x and y using base 8 [closed]

Question

In finding the values of x and y, if (x567) + (2yx5) = (71yx) ( all in base 8) I proceeded as under.

I assumed x=abc and y=def and followed.

  (abc+010 def+101 110+abc 111+101)=(111 001 def abc) //adding ()+()=() and equating LHS=RHS.
  abc=111-010=101 which is 5 in base 8 and then def=001-101 which is -4
  so x=5 and y=-4 

Now the Question is that the answer mentioned in my book is x=4 and y=3.