# Math Help - Algebra

1. ## Algebra

1. Max bought 5 notebooks and 4 pens. He spent a total of $10.65. Emily bought 3 notebooks and 3 pens for a total of$7.50. How much did the notebook and pens cost each.

2. Mr. Smith inherits $45,000. He invests part of the money into mutal funds giving him 4% return, and he invests the other part at the stock markets giving him 6%. At the end of the year he earned$2430 of interest. How much did he invest in both accounts?

1. This is what I did.
-3(5n+4p=10.65)
4(3n+3p=7.50)

-15n -12p= -31.95
12n +12p= 30.00
-3/3 1.95/3

-15n -12(.65) -31.95
-15n - 7.80 - 31.95 I added 7.80 and divided by -15
N=1.61 P=.65
What did I do wrong?

I have no idea on # 2.

2. ## Number 2

The solution to the second problem is :

First create two equations...

.04x + .06y = 2430

and

x + y = 45000

solve for y in second : y = 45000 - x

substitute this in the first equation:

.04x + .06(45000 - x) = 2430

.04x + 2700 - .06x = 2430

-.02x = -270

x = $13,500.00 at 4% y = 45000 - 13500 =$31,500.00 at 6%

3. Originally Posted by rowdy3
1. Max bought 5 notebooks and 4 pens. He spent a total of $10.65. Emily bought 3 notebooks and 3 pens for a total of$7.50. How much did the notebook and pens cost each.

2. Mr. Smith inherits $45,000. He invests part of the money into mutal funds giving him 4% return, and he invests the other part at the stock markets giving him 6%. At the end of the year he earned$2430 of interest. How much did he invest in both accounts?

1. This is what I did.=====>your first part is ok
-3(5n+4p=10.65)
4(3n+3p=7.50)

-15n -12p= -31.95
12n +12p= 30.00
----------------------------------------------
-3n/3 = 1.95/3
n=.65 (The cost of one notebook)

Substitute n=.65 into 1st equation:

$5n+4p=10.65$

$5(.65)+4P=10.65$ *

$3.25+4p=10.65$

$4p=7.40$

$p=1.85$ (The cost of one pen)
--------------------------------------------------------------
-15n -12(.65) -31.95===>this is where you went South. You substituted the value you found for n into p. See * above.
-15n - 7.80 - 31.95 I added 7.80 and divided by -15
N=1.61 P=.65
What did I do wrong?

I have no idea on # 2.
See corrections between the ---------------