The phrase a number means an arbitrary variable. We can pick any letter a-z except for i and e. Let's choose x. Four times a number: 4x nine more than four times a numbrer 4x + 9 The phrase is means equal to. We set 4x + 9 equal to 25 as our algebraic expression: 4x + 9 = 25 If the problem asks you to solve for x, we type it in our math solver and get: x = 4
