The first step in solving for the missing variable is to move the known values to one side of the equation. In this case, we would move the -123 to the opposite side of the equation:174 - _ = -123174 + 123 = _When we add 174 and 123, we get 297. Thus, the answer is B) 297.In summary, to solve for the missing variable in a subtraction problem, the known variables should be moved to one side of the equation, and the missing variable should be isolated on the other side. In this instance, we know that the difference between 174 and the missing value will result in -123, so moving the -123 to the opposite side of the equation lets us add the known values, thus determining the missing variable.