Hi there! :)
<u>Answer:</u>
In order to maintain the same ratio, she should sell 18 band posters.
<u>Step-by-step explanation:</u>
<u>Initial ratio:</u>
Ratio is: 105 movie posters for 90 band posters = <u>105 : 90</u>
She sells 21 movie posters, which means that we are left with 105 movies minus the 21 she sold.
105 - 21 = 84 → She now has <u>84</u> movie posters.
In order to answer your question, you'll need to use the cross product method:
105 movie posters → 90 band posters
84 movie posters → X
<u>(90 × 84)</u> ÷ 105 = X
<u>7,560 ÷ 105</u> = X
72 = X ⇒ Number of band posters she should have left to maintain the same ratio.
She has 90 band posters :
90 <u>- X</u> = 72
Add "X" to each side of the equation → 72 + X = 72 + X
90 = <u>72</u> + X
Subtract 72 from each side of the equation → 90 - 72 = 18
<u>18 = X</u>
There you go! I really hope this helped, if there's anything just let me know! :)
