Do these ratios form a proportion
Last term, Theo earned an average score of 85 points on maths tests. So far this term, his average score is 20% lower. What is the average of Theo's scores this term?
to figure this out we have to figure 20% of 85 the way I would do it is find 10% of 85 which is 8.5 then I would times it by two which equals 17 and that is your answer.