Question

7 less than fifteen times a number

Answer 1

Let the no. be x
Then The equation will be

= 15x - 7

Answer 2

If we say number in algebra, it simply means that the number is a variable,  as well as it can be written as any letter, usually x, but in some beginning algebra courses is written as n.

So 15 times a number is the same thing as 15 multiplied by n. 15n  and then 7 less than that : 15n – 7