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x+y=1
y-z=-3
2x+3y+z=1

i KNOW THE ANSWERS I JUST DON'T KNOW HOW THE BOOK GOT THE ANSWERS . i 'VE TRIED MANY DIFFERENT WAYS AND I STILL DONT' UNDERSTAND IT PLEASE EXPLAIN IT.

i KNOW THAT I HAVE TO ADD EQUATION 2 AND THREE TO GET THE FOLLOWING

2X+3Y+Z=1
Y-Z=-3
IN ORDER TO GET
2X+4Y=-2

THEN I DON'T KNOW FROM HERE

There a couple ways to solve this. You have
x+y = 1
y-z =-3
2x+3y+z= 1

You could first show
x=1-y and z=y+3 and substitute them into the 3rd equation to get
2(1-y)+3y+y+3=1 and solve for y to get
2-2y+3y+y+3=1
5+2y=1 so 2y=-4 and y=-2
then put this into the first two equations to solve for x and z.

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