Question

ytry

Answer 1

so what is z when it is isolated from the first equation?

Answer 2

2x - 5y + z = 15 get z alone so subtract 2x and add -5y to both sides
z=15-2x+5y

Answer 3

so now we replace z into the 2nd and 3rd equations

Answer 4

and?

Answer 5

4x-y+3(15-2x+5y)=15 3x-2y+2(15-2x+5y)=13
4x-y+45-6x+15y=15 3x-2y+30-4x+10y=13
-2x-14y+45=15 -x+8y+30=13
-2x+14y=-30 -x+8y=-17

Answer 6

so those are the new system of equations

Answer 7

which in this case A