The equation given in the question is 2s + s + 12 = 132 3s + 12 = 132 3s = 132 - 12 3s = 120 s = 120/3 = 40 From the above deduction we can see that the value of the unknown variable comes out to be exactly 40. This is possible because there is a single unknown variable and a single equation to get the value of the variable from. So the correct option among all the options given in the question is option "D".