I'd suggest using "elimination by addition and subtraction" here, altho' there are other approaches (such as matrices, substitution, etc.).
Note that if you add the 3rd equation to the second, the x terms cancel out, and you are left with the system
- y + 3z = -2
y + z = -2
-----------------
4z = -4, so z = -1.
Next, multiply the 3rd equation by 2: You'll get -2x + 2y + 2z = -2.
Add this result to the first equation. The 2x terms will cancel, leaving you with the system
2y + 2z = -2
y + z = 4
This would be a good time to subst. -1 for z. We then get:
-2y - 2 = -2. Then y must be 0. y = 0.
Now subst. -1 for z and 0 for y in any of the original equations.
For example, x - (-1) + 3(0) = -2, so x + 1 = -2, or x = -3.
Then a tentative solution is (-3, -1, 0).
It's very important that you ensure that this satisfies all 3 of the originale quations.
Answer: 
<u>Simplify both sides of the equation</u>
<u>Subtract 5n from both sides</u>
<u>Subtract 15 from both sides</u>
The answer to this problem is 9 hopefully this helps you!
respuesta:primero verdadero
segundo : no
Answer:
Her weekly expenses is $234
Step-by-step explanation:
At $7.20 per kilogram
From selling 90 kg, she will have
$7.20 × 90
= $648
If her net profit is $414
To get her expenses, we subtract net profit from total income
$648 - $414
= $234
