Answer:
It contributes to the isolation of the variable
Explanation:
The Step 1 is
![3x+18=54\\3x+18-18=54-18](https://img.qammunity.org/2020/formulas/mathematics/middle-school/byaub7hd3o9v07s3x1l4iw6rt5xo5ut3vy.png)
Now, the step one helps to solve the equation because we need to isolate the variable, taking all the terms to the other side of the equality, and the first step is moving the term 18 to the other side. So, it contributes to the isolation of the variable, which is mandatory.