9 is one-third of a number x A number x can be written as x x one-third of a number x means we multiply x by 1/3: x/3 The phrase is means an equation, so we set 9 equal to x/3 to get our final algebraic expression of: x/3 = 9 If the problem asks you to solve for x, you type this algebraic expression into our search engine and you get: x = 27