twice the difference between x and 28 is 3 times a number The difference between x and 28: x - 28 Twice the difference means we multiply x - 28 by 2: 2(x - 28) The phrase a number means an arbitrary variable, let's call it x x 3 times a number: 3x The word is means equal to, so we set 2(x - 28) equal to 3x: 2(x - 28) = 3x