Mary had 80 fliers to post around town. Last week, she posted 1/4 of them. This week, she posted 3/5 of the remaining fliers. How many fliers has she still not posted?
So if she had put out 1/4 of them, 1/4 of 80 is 20. 80-20=60. Okay, now if she has 60 left and has 3/5 remaining, 1/5 of 60 is 12. 12*3=36. so 60-36=24. She has 24 fliers left.