Answer:
OK, so she started with 70 fliers.
Last week, she posted 2/5 of them. 2/5 of 70 is equal to 28, so she has 28 fliers less than she started with. 70-28=42.
This week, she posted 4/7 of the remaining fliers (42). 4/7 of 42 is equal to 24. So, she has 24 less than 42, so 42-24=18.
She still needs to post 18 fliers.
Hope this helps!!!