An aid for navigation and pilotage at sea is the lighthouse , a tower building or framework very familiar among the navigators, especially to those who sail by boat. This lighthouse serves as the compass for the navigators as it provides travelers and mariners information on the wind direction by displaying a light for their guidance. Lighthouses also provide coordinate location for small aircraft traveling at night.

Because of modern navigational aids, the number of operational lighthouses has declined to less than 1,500 worldwide. Lighthouses are used to mark dangerous coastlines, hazardous shoals away from the coast, and safe entries to harbors.

Just like the lighthouse, you will be introduced to the world of symbols that are used to convey ideas in Algebra. The concept of variables and algebraic expressions are basic in the study of Algebra. The use of variables and symbols become more meaningful when word phrases or verbal phrases are translated to mathematical phrases . Identifying the key phrases in verbal phrases facilitates translating them to mathematical phrases . This process is a prerequisite in solving word problems.