equation

The relationship stated in symbols with an equals sign, and this period's values written directly underneath each symbol. The substitution row is what makes it checkable: a reader can see which number went where, and object to one term without rejecting the whole rule.

The relationship stated in symbols with an equals sign, and this period's values written directly underneath each symbol. The substitution row is what makes it checkable: a reader can see which number went where, and object to one term without rejecting the whole rule.

Example

Best when the rule is arithmetic over a few named quantities and you want it auditable at a glance.