First, pull out a factor of

.

Notice that when

(which you can arrive at via the rational root theorem), you have

which means you can pull out a factor of

. Upon dividing you get

The rational root theorem will come in handy again, suggesting that

appears a second time as a root, which means

Now this is more readily factored without having to resort to the rational root theorem. You have

so in fact,

shows up as a root for a third time.
So, you have

Two roots are obvious,

and

(with multiplicity 3). The remaining two are given by
Not sure what this has to do with maths, but probably because it would mean that people would have to buy 2 packs of hot dog buns just to get 8 hot dog buns, which makes him more money?
Answer:
19. x > 7
20. x < 35
21.
22. 
23.
or 
24. 45r
25.
26.
27.
28.
Step-by-step explanation:
{y = x - 4
=> 2x+x-4=5 => 3x=9......<em>x=3</em>
{2x + y = 5 <em>y=3-4=-1</em>
<em>________________________________________________</em>
{<em>x+4y=6</em>
<em>{y=-x+3</em>
<em>=> x+4(-x+3)=6</em>
<em> x-4x+12=6</em>
<em>-3x=-6</em>
<em>x=2</em>
y=-2+3=1
y=1
___________________________________________________-
{x+2y=9
{x-y=3 .......x=3+y
3+y+2y=9
3y=6
y=2
<em>x=3+2=5</em>
<em>x=5</em>
<em>_________________________________</em>
<em />{3x-2y=9
{y=2x-7
3x-2(2x-7)=9
3x-4x+14=9
-x=-5
x=5
<em>y=2*5-7=10-7=3</em>
<em></em>y=3
<em />
<em>
</em>