Answer:
She should sell 20 band posters from total 80 to keep the maintain the same ratio.
Step-by-step explanation:
The total number of movie posters collector has  = 120
The total number of band posters collector has  = 80
The current ratio of movie poster : band poster  = 120 : 100
or, reducing the ratio further, we get
ratio of movie poster : band poster  = 6 : 5  ......  (1)
Now, the number of posters she wants to sell = 24
So, the remaining movie poster left = 120 - 24 Â = 96
Let us assume she sells m band posters to keep the ratio equal.
So, the number of band posters she is left with = 100 - m
⇒The ratio of movie poster left  : band poster  left = 96 : 100 - m  .. (2)
Now here as the ratio remains same after selling m band posters, so
[tex]\frac{6}{5}  = \frac{96}{100 - m} \\\implies 100 - m = 96 \times\frac{5}{6} =  80\\or, 100 - 80 = m\\\implies  m= 20[/tex]
or, m = 20
Hence, she should sell 20 band posters from total 80 to keep the maintain the same ratio.