Exercise algebra.equations.linear.balance
Description
Solve a linear equation using only balance rules.
Derivation
![](http://ideas.cs.uu.nl/images/external.png)
-21 == -7*x
⇒ algebra.equations.linear.flip-7*x == -21
⇒ algebra.equations.linear.balance.negate7*x == 21
⇒ algebra.equations.linear.balance.scale-to-one, factor=7x == 3