State whether the given expression is an equation or not. Give reason for your answer.Identify the variable in the given expresssion.
An equation is a mathematical statement that shows the equality of two expressions. An equation has an equal sign (=) between its left hand side and right hand side. Hence, 20−(10−5)=3×5 is an equation.
A variable is a letter that represents an unknown quantity which can take any value. There is no variable in the given equation.