Answer:
20.
Step-by-step explanation:
According to the word problem, Mary had 75 fliers and posted 1/3 of them last week.
[tex]75 *\frac{1}{3} =\frac{75}{3}[/tex]
[tex]\frac{75}{3} =25.[/tex]
Therefore, Mary posted 25 of them last week.
[tex]75-25 =50[/tex]
Mary has 50 fliers that she has not posted.
Then, this week, Mary posted 3/5 of the remaining fliers.
[tex]50*\frac{3}{5} =\frac{150}{5}[/tex]
[tex]\frac{150}{5} =30.[/tex]
Therefore, Mary posted 30 of the remaining fliers this week.
[tex]50-30=20.[/tex]
Therefore, Mary has 20 fliers that she still has not posted.