### Theory:

Equation:
Any equation is a condition on a variable. It is satisfied only for a definite value of the variable.
Consider the following equation $$x - 3 = 10$$.

Let us substitute a few values to $$x$$.

 Value($$x$$) Equation($$x - 3 = 10$$) Equation satisfied or not? $$5$$ $$5$$ $$-$$ $$3$$ $$=$$ $$2$$ No $$7$$ $$7$$ $$-$$ $$3$$ $$=$$ $$4$$ No $$9$$ $$9$$ $$-$$ $$3$$ $$=$$ $$6$$ No $$11$$ $$11$$ $$-$$ $$3$$ $$=$$ $$8$$ No $$12$$ $$12$$ $$-$$ $$3$$ $$=$$ $$9$$ No $$13$$ $$13$$ $$-$$ $$3$$ $$=$$ $$10$$ Yes

From the above tabular column, we can understand that the equation holds only to a specific condition.

Apart from $$13 - 3 = 10$$, none of the conditions is satisfied.
An equation always contains an 'equal to' ($$=$$) sign in between.
It means that the left-hand side (LHS) is equal to the right-hand side (RHS).

In a valid equation, LHS will always be equal to the RHS.
Example:
1. $$2m + 8 = 25$$

2. $$k - 6 = 52$$
Expression without an 'equal to' ($$=$$) sign is not considered an equation.
Example:
1. $$b > 5$$

2. $$h$$ $$×$$ $$78$$