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. These letters are called [[variable|variables]]. For example,  

Algebra uses letters that ''stand for'' numbers. These letters are called [[unknown|unknowns]]. For example,  

x + y = 11

x + y = 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:

By using unknowns, 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