The answer would be "Nine students each make 2 models of Mars and its moons. How many models did they make in total?" Since the answer is 18 and there are 9 students (and also since 18 can be divided into 9), you can divide 18 and 9 to get 2. This makes sense because if each student makes 2 models (as stated), there'd be a total of 18 models (as stated in the question you gave). Hope this helped!
The solution to the system of equations is (x, y) = (10, 14), where x is the number of 3-point questions and y is the number of 5-point questions. The appropriate choice is ... The test contains 10 three-point questions and 14 five-point questions. (2nd selection)
