Changes
Ordinary arithmetic deals with ''specific'' numbers, treated individually: 4 + 7 = 11.
Algebra uses letters that ''stand for'' numbers. These letters are called variables. For example,
x + y = 11
By using lettersvariables, algebra can go beyond individual number facts and express general relationships between ''sets'' of numbers. Thus, the equation above represents ''every pair'' of numbers that add up to 11:
*x could be 4 and y could be 7
*x could be 5 and y could be 6
*x could be 10 and y could be 1.
