I think it's 20. Sorry if it's wrong
Answer:
<h2>A. -2</h2>
Step-by-step explanation:
![\det\left[\begin{array}{ccc}a&b\\c&d\end{array}\right] =ad-bc\\\\\det\left[\begin{array}{ccc}3&-5\\1&1\end{array}\right] =(3)(1)+(-5)(1)=3-5=-2](https://tex.z-dn.net/?f=%5Cdet%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7Da%26b%5C%5Cc%26d%5Cend%7Barray%7D%5Cright%5D%20%3Dad-bc%5C%5C%5C%5C%5Cdet%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D3%26-5%5C%5C1%261%5Cend%7Barray%7D%5Cright%5D%20%3D%283%29%281%29%2B%28-5%29%281%29%3D3-5%3D-2)
Divide through everything by <em>b</em> :

Since <em>a/b</em> < <em>c/d</em>, it follows that

Multiply through everything on the right side by <em>b/d</em> to get

and so (<em>a</em> + <em>c</em>)/(<em>b</em> + <em>d</em>) < <em>c/d</em>.
For the other side, you can do something similar and divide through everything by <em>d</em> :

and <em>a/b</em> < <em>c/d</em> tells us that

Then

and so (<em>a</em> + <em>c</em>)/(<em>b</em> + <em>d</em>) > <em>a/b</em>.
Then together we get the desired inequality.
Answer:
"In word" as in word form?
3/4 = three fourths
1/5 = one fifth
3/4 = three fourths (again?)
1 3/5 = one and three fifths