Theory:

An equation may be an equality statement between two mathematical expressions of one or more variables.
Simple linear equations play an important role in many situations involving real numbers it helps to solve more complex problems. The following situation allows us to see how simple equations can help solve a problem.
Example:
Anu's dad's age is \(10\) years older than three times of Anu's age. What is the age of Anu if the age of his dad is \(40\)?
 
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Let's assign a variable first.
 
Let Anu's age be '\(x\)' years.
 
Now, the age of Anu's dad is \(10\) years higher than three times of Anu's age. Therefore we get the following:
 
Dad’s age \(= 10 + 3x\). Dad’s age is given as \(40\).
 
Therefore, we will equate and get: \(10 + 3x = 40\).
 
Now, this is called a simple linear equation. It can simplify problems and help us find Anu’s dad age by just substituting Anu’s age in place of \(x\).