[FEATURE] Linear equation solver

[tommens]

Describe the new functionality you would like to see
Provide support for specifying and solving linear equations with one or more variables. The required functionality should include:

• A textual user interface to represent linear equations and their solutions.
• A visual user interface to represent linear equations and their solutions.
• Appropriate reporting and/or error handling in case the set of linear equations provides no solution or multiple solutions, or in case of syntactic errors in the equations.

Illustration
The figure below provides a possible illustration of what a visual interface for linear equation solving could look like.