how do i do this problem, in desc

Question

X+ 2y =12

3y- 4z = 25 

x+ 6y + z = 20 

with elimination method

Answer 1

There are different approaches to solving the problem. Here is one of them.

 

x+2y=12

3y-4z=25

x+6y+z=20

 

take the first equation

x+2y=12

x=12-2y

 

take the second equation

3y-4z=25

-4z=-3y+25

4z=3y-25

z=(3/4)y-25/4

 

take the third equation and substitute the new second and the new first equations

x+6y+z=20

12-2y+6y+(3/4)y-25/4=20

multiply by 4 to eliminate the fractions and simplify after that

48-8y+24y+3y-25=80

23+19y=80

19y=80-23

19y=57

y=57/19

y=3

using the first equation

x+2y=12

x+2(3)=12

x+6=12

x=6

using the last equation

x+6y+z=20

6+6(3)+z=20

6+18+z=20

24+z=20

z=-4

x=6, y=3, z=-4