Answer:
600
Explanation:
Andrew has 280 points. We are told that he is 20 points short of 50% proficiency.
280 + 20 = 300
Now we know that 300 is 50% of the maximum amount of points.
As 50% is equal to 1/2, we know that 300 is 1/2 of the total. To find the total, we must double 300, resulting in 600.
Hope this helps!