The equations have operations, variable, an equal sign in common.
What is an Equation?
An equation is a mathematical expression that contains an equals symbol.
As per the definition, the equation contain operations, variable, an equal sign. That means whatever be the equation then it must contain operations, variable, an equal sign.
So, all the equations have operations, variable, an equal sign these three things in common.
For example: 4a+b=0
Learn more about equation here: