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:
The best estimate of the area of the larger figure is 
Step-by-step explanation:
step 1
<em>Find the scale factor</em>
we know that
If two figures are similar, then the ratio of its corresponding sides is equal to the scale factor
Let
z----> the scale factor
x-----> the corresponding side of the larger figure
y-----> the corresponding side of the smaller figure
so

we have


substitute
-----> the scale factor
step 2
<em>Find the area of the larger figure</em>
we know that
If two figures are similar, then the ratio of its areas is equal to the scale factor squared
Let
z----> the scale factor
x-----> the area of the larger figure
y-----> the area of the smaller figure
so

we have


substitute and solve for x

So it's multiple choice?
whichever looks most like this is the answer:
30mn+6n-36m