Question 60688
If the first equation is x+3y=0, then your error is in this step:
them i multiplied 10 to the second row and added the product to the third row and got
1 3 0 / 0
0 1 -1/2 / -1/2
0 0 -6 / 16

The last number should be 11-5=6, not 16.