Answer:
 The difference of fifty-four and seven times a number is written as 54 - 7x.
Step-by-step explanation:
Given: expression “the difference of fifty-four and seven times a number”
We have to write the given algebraic expression represents “the difference of fifty-four and seven times a number” 
Consider the given algebraic expression represents “the difference of fifty-four and seven times a number”
Let the number be x 
Then, seven times a number is 7x 
And the difference of fifty-four and seven times a number is written as 54 - 7x.
Thus, The difference of fifty-four and seven times a number is written as 54 - 7x.