What is the solution to this system of equations?

x − 2y = 15
2x + 4y = -18

y=-6 ;  x=3

Step-by-step explanation:

x − 2y = 15

2x + 4y = -18

x − 2y = 15

  +2y .   +2y

x=2y+15

2(2y+15) + 4y = -18

4y+30+4y=-18

8y+30=-18

    -30 .  -30

8y=-48

y=-6

x=2(-6)+15

x=-12+15

x=3

4 and 5)16.97 or 12√2

6)15.59 or 9√3

7)y = 15.59 or 9√3     x =27

8)17.80

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step-by-step explanation: