Need help with some math problems

[speed02]

here is a word problem if someone can post how to set it up and the answer that would be great because i have to do the work any way. I did like 30 problems already and these are the only ones im having a problems with.

Problem #1 Its in a Linear systems/matrices chapter
there are 150,000 registered democrats, Republicans, and Indepdents in a country. the number of indep. is 20% of the total number of Demo. and Rep.. In an election, 40% of the Demo. voted, 50% of the Rep., and 70% of the Indep.. The votess totaled 72,000. How many Democrats, Republicans and Independents are registered?

Problem #2 summarize the given information in matrix form
AN appliance saleswomen sold 15 washers, 8 dryers, and 13 microwave ovens in March. She sold 12 washers, 11 dryers and 6 microwave ovens in April.

Problem #3
The health fare cereal Co. makes three cereals using wheat, oats, and raisins. The proportions of each cereal are.

cereal wheat oats Raisins

Lite .75 .25 0
trim .50 .25 .25
Health Fare .25 .50 .25

use matrix Multiplication to determine the number of pounds of wheat, oats, and raisins needed to fill an order of 1480 pounds of Lite, 1840 pounds of Trim and 2050 pounds of health Fare.


Thanx in advance for the help.

 

[arthur ohlsten]

the 3 equations are:
R+D+I=150,000
.2[R+D]=I
.4D+.5R+.7I=72,000

for AX=K in matrix notation X=A^-1 K

1 1 1
A= .2 .2 -1
.5 .4 .7


R
X=D
I

150,000
K=0
72,000

you should be able to find A inverse and multiple it with K
Arthur