Question

-x+3y=-72 & 3x+4y-4z=-4 & -20x-12y+5z=-50​

Answer 1

Answer:

3y-x=72 --------(I)

3x+4y-4z=-4 ------(II)

So, (I)×5

5(3x+4y-4z)=-4×5

or, 15x+20y-20z= -20 -------- (III)

-20x-12y+5z=-50 ------(IV)

So, (IV)×4

4×(-20x-12y+5z)=4×-50

or, -80x-48y+20z=-200 -------(V)

So, (III)+(V)

15x+20y-20z-80x-48y+20z= -20-200

or, -65x-28y=-220 -----(VI)

So,(I)×65

65(3y-x)=72×65

or, 195y-65x=72×65 -------- (VII)

So, (VI)-(VII)

or, -65x-28y-195y+65x=-220-4670

or, -223y=-4890

or, y= 4890/223