How do you write a variable expression for the word phrase “$9\text{ less than k}$” ?

Hint: In this question, we have to write a sentence in variable expression from a word phrase. We have mathematics in our day-to-day life. Converting our daily life things into mathematical language leads to variable expressions. As we know, a variable expression is an expression that contains variables along with numbers and mathematical operations to define an expression. So, we solve this question by taking an example and get the required solution in terms of a variable expression.

Complete answer:
In this question, we have to write a word phrase into a variable expression.
A variable is a symbol that is denoted by an alphabet. It is a function, used for varying expressions or quantities to represent an arbitrary element. Examples of variables are $x,\text{ }y\text{, }z\text{, }p$ and so on. Also, a variable expression consists of some variables with constants and any of the four mathematical operations that are division, multiplication, addition, and subtraction. Whenever a word phrase is given to us, we can change that sentence into a variable expression that is in terms of a mathematical language.
So we will solve this problem by taking an example.
Let us suppose that Sita is the mother of Rakesh and they both went to the supermarket, to buy some fruits and vegetables for dinner. Rakesh is a 5th class student, so he is very curious about buying vegetables.
So they both went to a shop and bought 9 tomatoes. From those 9 tomatoes, they give 5 of them to a beggar. At that very moment, his son asked his mother how many tomatoes they are left with. So, his mother helps him in solving his doubt.
She said let us suppose I have $9$ tomatoes with me, and we give $1$ tomato to the beggar.
Thus, in return, they are left with $8$ tomatoes. His son got confused and therefore, his mother explained to him more.
She said, if we make a sentence, it will be: $\text{1 less than 9}$ tomatoes, and when we convert into mathematical language that is in terms of an equation, we get
$9-1$ tomatoes, which is equal to $8$ tomatoes --------- (1)
Again, she said that now, I give $2$ tomatoes to the beggar.
Thus, sentence formation for the above line is $\text{2 less than 9}$ tomatoes, and when we convert it into mathematical language, we get
$9-2$ , which is equal to $7$ tomatoes.
Again, she said that now, I give $3$ tomatoes to you , so I left with 6 tomatoes, that is
Sentence formation will be: $\text{3 less than 9}$ tomatoes, and when we convert it into mathematical language, we get
$9-3$ , which is equal to $6$ tomatoes.
Therefore, if I have $k$ tomatoes and I give $9$ tomatoes to him, how many tomatoes are left with me?
So, his son said the sentence formation will is $\text{9 less that k}$ tomatoes, and in the mathematical form that is in terms of variable, where k is some variable, it is
$k-9$ tomatoes, which is our required answer.
Thus, we came upon the result that we can write a word phrase $\text{9 less than k}$ into a variable expression as $k-9$.

Note: Always, remember that less than means subtracting. If I say a is less than b, implies that we are subtracting a from b, that is $b-a$ , and not subtracting a from b.