# Solving systems of equation

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• Nov 20th 2012, 02:08 AM
asilvester635
Solving systems of equation
I really don't know how to solve this system of equation, it's nothing I've ever done before.... mostly they would have identical and the same amount of variables in every column but this one doesn't....

x + 10 + y + 36 = 210
80 + 10 + z + y = 180
36 + z + y + t = 220
• Nov 20th 2012, 02:12 AM
MarkFL
Re: Solving systems of equation
Collect like terms, then it will be in a somewhat more familiar format.
• Nov 20th 2012, 02:37 AM
asilvester635
Re: Solving systems of equation
10x + 36y = 210
80z + 10y = 180
36z + yt = 220

LIKE THAT???
• Nov 20th 2012, 02:42 AM
grillage
Re: Solving systems of equation
No, not like that. You have switched some additions to multiplications. Let's take the first one: x + 10 + y + 36 = 210 where we can subtract the 10 and the 36 from both sides to give x + y = 164. Follow that process with the other two and see where it takes you.
• Nov 20th 2012, 02:45 AM
asilvester635
Re: Solving systems of equation
x + y = 164
z + y = 90
z + y + t = 184

like that??? if it is, then now what?
• Nov 20th 2012, 02:46 AM
MarkFL
Re: Solving systems of equation
No, we cannot change addition to multiplication like that.

We have:

$x+10+y+36=210$

$80+10+z+y=180$

$36+z+y+t=220$

Now, if we subtract all the constants on the left side of each equation from the right side, the system becomes

$x+y=164$

$z+y=90$

$z+y+t=184$
• Nov 20th 2012, 02:50 AM
grillage
Re: Solving systems of equation
Look at equations 2 and 3. Is it not obvious what t is now?
• Nov 20th 2012, 02:56 AM
asilvester635
Re: Solving systems of equation
ohhhhhhhh...
• Nov 20th 2012, 02:57 AM
asilvester635
Re: Solving systems of equation
okay so t is equal to 94....

so can i take out the variable t out from the second and third equation and solve the second and third equation like a regular systems of equation?
• Nov 20th 2012, 03:03 AM
grillage
Re: Solving systems of equation
Well t only appears in the 3rd equation. Using the 1st and 2nd equations I cannot see how you can solve for x, y and z. It seems like you are missing some information.
• Nov 20th 2012, 03:05 AM
MarkFL
Re: Solving systems of equation
You will have to solve for two of the remaining variable in terms of the third.
• Nov 20th 2012, 03:18 AM
asilvester635
Re: Solving systems of equation
actually there's 3 variables remaining.... this is so hard
• Nov 20th 2012, 03:27 AM
MarkFL
Re: Solving systems of equation
Yes, I mention 3 remaining variables. You will have to express 2 of them in terms of the third.

We know $t=94$. So this leaves:

$y=164-x$

$z=90-y=90-(164-x)=x-74$

This is one way to express the solution, can you find another?
• Nov 20th 2012, 03:29 AM
asilvester635
Re: Solving systems of equation
Well this was my original question

Probability and Statistics homework problem question
Example 1: Computers, fine arts, economics - this one requires using system of equations

There are 500 seniors.
210 are enrolled in computers
80 do not need any of the 3
80 are taking only fine arts.

180 are taking fine arts.
36 taking only economics and computers
10 taking only fine arts and computers
220 taking economics

Find:
1.) P(only taking economics)
2.) P(economics and fine arts)
3.) P(taking all 3 classes)

Then this guy gave me this answer
(View the picture to understand how i got the system) So, you have

the system
1) x + 10 + y + 36 = 210
2) 80 + 10 + z + y = 180
3) 36 + z + y + t = 220
4) x + 10 + y + 36 + t + z + 80 = 420

4 Systems, 4 variables, solve

Attachment 25820
• Nov 20th 2012, 03:43 AM
MarkFL
Re: Solving systems of equation
Okay, the diagram is correct, but leaves out the 80 not taking any of the 3. The system I get is:

$x+y+z+t=294$

$x+y=164$

$y+z=90$

$y+z+t=184$

Now you have 4 equations and 4 unknowns.
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