I think a much better reason for knowing fractions is that the techniques you learn for fractions are exactly the same ones you will need for parts of algebra. If you don't understand and master the ideas for fractions, then you will find learning algebra difficult.lgebra involves quantities called variables (that can represent values perhaps not yet known). One kind of formula in algebra that has one or more variables is called a rational expression. Adding and subtracting rational expressions is just like adding and subtraction fractions-you need to use a common denominator.