Answer:
![[0, 3, -6]](https://tex.z-dn.net/?f=%5B0%2C%203%2C%20-6%5D)
Step-by-step explanation:
{4x + y = 3
{x + y - z = 9 ←
{2x + 2y + z = 0 ←
{4x + y = 3
{3x + 3y = 9 >> Combined equation
−¾[4x + y = 3]
{−3x - ¾y = −2¼ >> New Equation
{3x + 3y = 9
_________
2¼y = 6¾
___ ___
2¼ 2¼
[Plug this back into all three equations to get the z-value of −6, and the x-value of 0]; 
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Answer:
89/100
Step-by-step explanation:
The average weighted by the number of students is ...
(90(0.90) +10(0.80))/100 = (81 +8)/100 = 89/100
D is the answer because it says each and that’s a key word to understand that it’s multiplying
