When 9 is subtracted from 5 times a number ,the result is 31 A number means an arbitrary variable, let's call it x. 5 times this number is written as 5x. 9 subtracted from this is written as 5x - 9 The result means we have an equation, so we set 5x - 9 = 31. This is our algebraic expression. Now if we want to solve for x, we plug this equation into the search engine and get x = 8.