mcrawley25 Posts: 1, Reputation: 1 New Member #1 Oct 30, 2011, 03:30 PM
system of equations
The sum of three numbers is -2. The sum of three times the first number, twice the second number, and third number is 9. The difference between the second number and half the third number is 10. Find the numbers.
 Unknown008 Posts: 8,076, Reputation: 723 Uber Member #2 Oct 31, 2011, 12:32 AM
The sum of three numbers is -2.

Let's say the 3 numbers are a, b and c.

So, their sum becomes:
a + b+ c = -2

The sum of three times the first number, twice the second number, and third number is 9.

That means this, right?
3a + 2b + c = 9

The difference between the second number and half the third number is 10.
b - 0.5c = 10

Right?

You have 3 equations and 3 variables, can you solve them?

Hint: Try using the first two equations to eliminate a, then use the result to simultaneously solve for b and c using the third equation.
 taxesforaliens Posts: 649, Reputation: 117 Senior Member #3 Oct 31, 2011, 08:21 AM
You would first need to set up the system of equations:

The sum of three numbers is -2
a+b+c=-2
The sum of three times the first number, twice the second number, and third number is 9
3a+2b+c=9
The difference between the second number and half the third number is 10
b-0.5c=10

Does that help? Give us he solution you get.

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