ANSWER
a. A variable is an unknown number or value represented by a letter
EXPLANATION
In mathematics, we use letters to represent an unknown quantity or number.
For instance, we can use the letter , t, to represent time taken to cover a given distance.
We can use the letter , s, to represent displacement or distance covered by an object.
The letters that we use to represent the unknown values or numbers are called variables.
The correct answer is A.
