Help with an equation

Tell them to look at an equation as a balanced set of scales.
Provided you do the same thing to the left and right scales you
won't disturb the balance.
You can add or subtract the same weight from both scales and it will remain balanced'.
You can double the weight on the right scale and provided you double the weight on the left scale , they will remain balanced.
To solve any equation you have to juggle weights so that the
unknown value is in one scale (it doesn't matter which) and the
known values in the other.
In this equation you could subtract the weight 3 from both scales.
Then subtract the weight 4w from both scales to get the unknown
w on its own in one scale and it turns out that w has the same weight as 6.