Answer:
4
Explanation:
Last week she posted 2/3 of the 42 fliers. This means she posted (2/3)*42 fliers.
(2/3)*42
84/3
28
So she posted 28 last week.
So of the 42, 42-28=14 remain
This week she posted 5/7 of the remaining fliers.
So she posted 5/7 of the 14 that remainder. This means she posted (5/7)*14 fliers.
(5/7)*14
70/7
10
So she posted 10 this week.
So of the 42, 42-28-10=4 remain.
She hasn't posted 4 fliers.