# Subtract from Sides

<p class="callout info"><span style="white-space: pre-wrap;"><b>What</b>: Subtract the same expression from the both sides of ==  
<b>Why</b><span style="white-space: pre-wrap;">: Such side-wise subtraction is an essential computation for solving equations </span>  
<b>Time to Complete</b><span style="white-space: pre-wrap;">: 3 hours </span></p>

```
eq = (x -3 == 17*y + 9);

lhs = eq.left - 9; 
rhs = eq.right - 9;

eq2 = (lhs == rhs);

show eq2;

save as sides;
```

Output

"eq2" → -12 + x == 17*y

**Output**

   <style>
        .box {
            width: 200px;
            height: 70px;
            background-color:  hsla(89, 43%, 51%, 0.3);
            border: 2px dotted orange;
            padding: 10px;
            margin: 10px;
        }
    </style>

<div class="box">
  "lhs" → (-12 + x)/17
  <br>
"rhs" → y
</div>


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