If you simply solve the equation for w, rather than "guess and check" using the values in the "replacement set," you find ...
... 6w +6 = 60 . . . . simplify the equation
... 6w = 54 . . . . . . . subtract 6
... w = 9 . . . . . . . . . divide by 6
The appropriate choice is ...
... D. 9
