Changes

Ordinary arithmetic deals with ''specific'' numbers, treated individually: 4 + 7 = 11.

Ordinary arithmetic deals with ''specific'' numbers, treated individually: 4 + 7 = 11.

Algebra uses letters that ''stand for'' numbers. For example,  

Algebra uses letters that ''stand for'' numbers. These letters are called variables. For example,  

x + y = 11

x + y = 11

By using letters, 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:

By using variables, 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 4 and y could be 7

*x could be 5 and y could be 6

*x could be 5 and y could be 6

*x could be 10 and y could be 1.

*x could be 10 and y could be 1.