What is an equation. Choose from the options given below.
(a) A statement in which the values of two mathematical expressions are equal.
(b) An expression that computes the value of variables.
(c) A mathematical expression.
(d) None of these.

Hint: We will start to solve this question by first of all defining what is an equation and then going for matching from the options given below and neglecting or cancelling the options which do not hold true for the definition of an equation.

Complete step-by-step solution -

An equation is a statement that the values of two mathematical expressions are equal (indicated by the sign =).
Observing from the options given below we see that the definition of equation in the first option is given by a statement in which the values of two mathematical expressions are equal. This is the correct definition of the equation because in an equation we go for equating two mathematical expressions by an equal sign.
Therefore, option (a) holds true for the definition of an equation.
Now we will go for checking the rest of the given options.
Now we go to observing the second option. The second option states that the definition of an equation is “an expression that computes the value of variables. This is wrong because an equation does not satisfy the criteria to find or compute a variable, it's just a statement which makes two mathematical expressions equal by the equality sign.
So, the second option, that is, option (b) is wrong.
Similarly, option (c) and option (d) are also wrong.
Therefore, we got the correct answer as option (a).

Note: The possibility of error in this type of question can be just checking first or one option from the given options and verifying that it is true. This method is wrong because all the other options can also satisfy the criteria. Always go by picking one option simultaneously and checking if it is correct or not.