Exercise algebra.equations.linear.balance

Description
Solve a linear equation using only balance rules.

Derivation

-6 == -13*x-15

⇒ algebra.equations.linear.balance.con-left-plus, term=15

9 == -13*x

⇒ algebra.equations.linear.balance.scale-to-one, factor=-13

-9/13 == x

⇒ algebra.equations.linear.flip

x == -9/13