When numbers are replaced by letters it opens up new opportunities. We're no longer fixed by set values and specific problems. Algebra opens up mathematics by abstracting set problems and making them relevant for general situations. Learning the notation of algebra prepares the way for great opportunities.
Prior Knowledge & Skills
Numeracy is very important as we still use numbers in algebraic expressions. Knowledge of integer arithmetic and order of operations makes the abstraction of algebra easier to come to terms with. Without these numeracy skills students can be slowed with their comprehension and numerical errors can lead to frustration.
Start off simple with short expressions. Alter the letters and increase the numerical difficulty. Introduce powers and brackets to form quadratic expressions. Look at equations, equality, and inequality. Look at applying algebra to solve problems and model situations.
Often considered a purer form of maths, just used by mathematicians, but this is far from the truth. Every day millions of lines of computer code are generated from basic algebraic equations. Scientists, engineers and accountants apply formulae to work out critical values in their work day. Oh, and yes, mathematicians and researchers do use algebra to carve out new theories and proofs.
Get an idea of algebra from this PowerPoint: