If the math equation you're doing has letters or other symbols that stand for numbers, you're likely doing *algebra*. You probably took your first *algebra* class early in your high school years.

The noun *algebra* comes from Arabic word *al jebr*, meaning "reunion of broken parts," which appeared in the title of mathematician al-Khwarizmi's famous book on equations. In algebra you use basic arithmetic like addition and subtraction, but the quantities you're working with are often unknown — that's why they're represented by letters. You might remember solving algebra equations that look like this: a(b + c) = ab + ac. The letters a, b, and c all represent a number.