To start to figure this problem out, we can first figure out how many more pages you read in an hour compared to your sister.
50 - 40 = 10, so you read 10 more pages in 1 hour.
Now we have to figure out how much more you would read in 1/2 an hour. Since 1/2 an hour is 1/2 of an hour, we can divide 10 by 2 to figure out how many more pages you read in an hour compared to your sister. 10 divided by 2 is 5, so you read 5 more pages every half hour.
First you had to remove parenthesis first.

Multiply by the numbers.

Final answer 



Hope this helps!
And thank you for posting your question at here on brainly, and have a great day.
-Charlie
Answer:
Step-by-step explanation:
<u>Given:</u>
- AB = 192 cm
- AC : CB = 1 : 3
- CD = BC/12
- The distance between midpoints of AD and CB = x
<u>Find the length of AC and CB:</u>
- AC + CB = AB
- AC + 3AC = 192
- 4AC = 192
- AC = 192/4
- AC = 48 cm
<u>Find CB:</u>
<u>Find the length of CD:</u>
- CD = BC/12 = 144/12 = 12 cm
<u>Find the length of AD:</u>
- AD = AC - CD = 48 - 12 = 36 cm
<u>Find the midpoint of AD:</u>
<u>Find the midpoint of CB:</u>
- m(CB) = AC + 1/2CB = 48 + 144/2 = 48 + 82 = 130 cm
<u>Find the distance between the midpoints:</u>
The ratio of 7200 to 6400 equals 1.125 in decimal form. I hope this helps!:)