I need help with some math problems?

Question

I know i should do my own homework, but i just CANNOT find the answers in my book. so don't bash me about how i should do my homework, because i do. but i just can't get these. so if you can, help me. if you can't or wont, then move on to the next question.

P.S:::: if you could explain how to do them so i know the next time, that would be great.

#1 : 18/8 = 108/x

#2 : 7/3 = x+3/4

#3 : 3x + 2 > 11 OR 3x - 2 < -4

#4 : -13 < 3x + 5 < 26

#5 : Sam has a total of 43 quarters and nickels in her purse. If her change is worth $7.75, how many nickels and how many quarters does Sam have?

Answer 1

1.  Cross multiply to get:

18x = 8*108

Divide by 18:

x = 8*108/18 = 48

2. subtract 3/4 from both sides:

7/3 - 3/4 = x

Find the common denominator:

28/12-9/12 = x

Simplify:

19/12 = x

or 1 7/12 = x

3. Solve each separately:

3x + 2 &gt; 11

3x &gt; 9

x &gt;3

3x - 2&lt; -4

3x &lt; -2

x &lt; -2/3

That means that either x is bigger than 3 or it&#039;s less than -2/3

4. Usually in algebra, we do the same thing to both sides.  Here, we do the same thing to all three side:

-13 &lt; 3x + 5 &lt; 26

-18 &lt; 3x &lt; 21

-6 &lt; x &lt; 7

5. Use each piece of information to set up an equation:

q + n = 43

25q + 5n = 775 (note: $7.75 = 775 cents)

There&#039;s more than one way to do the algebra from here, but here&#039;s one way:

multiply the first equation by (-5)

-5q - 5n = -215

Line up the two equations:

25q + 5n =  775

-5q  - 5n = -215

Add the equations together:

20q = 560

q = 28

Plug q = 28 into one of the original equations:

28 + n = 43

n = 15