Hello! I can help you with this! To write a proportion for this situation, you set it up like this:
x/50 = 40/100.
We set the proportion up like this, because we are looking for the amount of points out of 50 needed to get a score of 40% on the test. Cross multiply the values diagonally in order to get 100x = 2,000. Now, divide each side by 100 to isolate the "x". 2,000/100 is 20. x = 20. A student needs to get 20 points out of 50 points in order to get a score of 40%. The answer is 20.