Answer:
third option (7.5, 8)
this option (6, 5, -3)
Step-by-step explanation:
you eliminate one variant by expressing it through the other(s) until you have one equation with one variable.
that you solve, and then you go back to the other elimination expressions to calculate the others.
2x - y = 7
-2x + 3y = 9
since the terms with x are already so similar, we could now simply add both equations and solve that result :
2x + (-2x) -y + 3y = 7+9 = 16
0×x + 2y = 16
2y = 16
y = 8
=>
2x - 8 = 7
2x = 15
x = 7.5
x - 2y - 3z = 5
x + 2y + 3z = 7
x + z = 3
the same trick by adding the first 2 equations
x + x -2y + 2y -3z + 3z = 5 + 7 = 12
2x + 0y + 0z = 12
2x = 12
x = 6
=>
6 + z = 3
z = -3
and then
6 + 2y + 3(-3) = 7
6 + 2y - 9 = 7
2y - 3 = 7
2y = 10
y = 5
