9x+y=16
x-y=0
i have to solve by elimination.
will someone me ?

To do elimination, you combine the two equations by adding
  -9x + y = 16
+  x  -  y  = 0
 -8x  + 0y = 16

Now that there are 0y, we can solve for x:
-8x = 16
divide both sides by -8 
x = -2

To solve for y, plug the answer you got for x in to the original equations.

-9x + y = 16
-9(-2) + y = 16
18 + y = 16
y = -2 

x - y = 0
-2 - y = 0
y = -2

x = -2 and y = -2