In order to solve this problem you MUST know the INVERSE PROPERTY RULE. It’s pretty simple. For example in this problem x/9=3, what is 9 doing to the x? It’s dividing it. And the opposite of dividing is multiplying. So in order to isolate the x you must multiply 9 on both sides. Because whatever you do on one side you must do to the other. So far your equation should look like this: 9*x/9=3*9. And the 9/9 cancel each other out. Leaving x=3*9. And that will be 27. So x=27.
The error they made here was that they didn’t they didn’t multiply 9 on BOTH sides just on one. Leaving this problem incomplete.