Definition
Unknown value
An unknown value is a value not given directly but fixed by an equation or condition.
What it means
The symbol is a stand-in, not the answer. Look at the relationship around it and find the value that makes the whole statement true. In one equation, the unknown may have one fixed value.
Remember it
Treat the symbol like a covered value; use the relationship to uncover it.
Example
In 5 × △ = 35, the triangle stands for an unknown value. Since 35 ÷ 5 = 7, △ = 7.
Watch for
An unknown is not always the same as a variable. A variable may be allowed to take many values, while this equation fixes one value.
Common mix-up
The mark that represents the unknown is not itself the value; different marks can stand for the same number.
Exact meaning
An unknown value is a number or other mathematical value that is not given directly but is constrained by an equation or condition. A blank, box, question mark, or letter can represent it.