6 plus twice the sum of a number and 7. The phrase a number mean an arbitrary variable, let's call it x. The sum of a number and 7 means we add 7 to the variable x. x + 7 Twice the sum means we multiply the sum by 2: 2(x + 7) 6 plus means we add 6 to 2(x + 7) 6 + 2(x + 7)