How do you define a variable and write an expression for each phrase: eight minus the product of 9 and a number?
We can choose any variable to represent "the number" being referred to.
Let the number be
The word product (meaning multiply is always used with the word "AND", telling us which twp values are being multiplied together.
In this case, "The product of 9 and a number"
"8 minus ..... " means subtract something from 8.
IN this case it is what we have written above that is being subtracted FROM 8.
(Because of the order of operations, the multiply would happen before the minus.)