Twice the difference between a number, x, and eighteen is three times the number.

Answer 1

18-2x=3x. twice the difference between a number x and eighteen should mean that twice the difference of x is -2x and "between two numbers" means 18-2x, which includes 18, while "is" indicates equality with "three times the number x" which is 3x and all of the aspects of the description accumulating into 18-2x=3x.