Can you please help me solve questions 18 and 20 by using substitution or elimination method.

http://img230.imageshack.us/img230/4372/mathyv1.jpg

Thanks :)

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- October 3rd 2006, 11:44 AMdgolverkMoney problems
Can you please help me solve questions 18 and 20 by using substitution or elimination method.

http://img230.imageshack.us/img230/4372/mathyv1.jpg

Thanks :) - October 3rd 2006, 12:11 PMCaptainBlack
- October 3rd 2006, 12:33 PMdgolverksorry about that...
here are the questions:

1)You are starting a business that sells air filters for homes. Your startup costs for the business are $1250 and each air filter kit costs $40.

If you sell the filters for $60, how many must you sell to break even?

2)If you buy 7 hmaburgers and 3 slices of pizza from Sizzler, you get $1 change from $20 bill. If you buy 8 hamburgers and 2 slices of pizza, you get $0.50 back from a $20 bill. How much change would you get from a $20 bill if you bought 3 slices of pizza and 5 hamburgers?

Thanks again! - October 3rd 2006, 02:10 PMQuick
I will use "substitution" since I believe that's what your teacher wants...

The amount of money you pay equals $1250 plus $40 per filter.

y=the amount of money

x=filters

Thus you have equation:**y=40x+1250**

The amount of money you make is equal to $60 per filter:**y=60x**

To braek even, the amount of money you make must equal the amount of money you spent, thus:**40x+1250=60x**

now subtract both sides by 40x:**1250=20x**

Now divide both sides by 20:**62.5=x**

So you need to sell 62.5 filters to break even, which you can't do, so you sell 30 filters to break even.

Quote:

2)If you buy 7 hmaburgers and 3 slices of pizza from Sizzler, you get $1 change from $20 bill.

**7h+3p=19**

Solve for p to get:**p=(19-7h)/3**

Quote:

If you buy 8 hamburgers and 2 slices of pizza, you get $0.50 back from a $20 bill.

**8h+2p=19.5**

Solve for p to get:**p=(19.5-8h)/2**

Substitute:**(19-7h)/3=(19.5-8h)/2**

solve for h, then substitute that value into one of the equations to find the price of hamburgers, than subtract the price of 3 slices of pizza and 5 hamburgers from 20. - October 3rd 2006, 02:44 PMdgolverk
Thanks! :)