X+y-z=5 - x-4y-8z=6 3x+5y-4z=-20

x = 24.48, y = - 15.52, z = 3.95 to the nearest hundredth.

Step-by-step explanation:

x+y-z=5 (a)

-x-4y-8z=6 (b)

3x+5y-4z=-20 (c)

Adding equations a and b:

-3y - 9z = 11 (d)

Now multiply equation b by 3:

-3x - 12y - 24z = 18 (e)

Adding c and e:

-7y - 28z = - 2 (f) Multiply by 3 to give (g)

-3y - 9z = 11 (b) Multiply by - 7 to give (h)

-21y - 84z = - 6 (g)

21y + 63z = - 77 (h) Adding g and h:

-21z = - 83

z = 3.952

and y is found bt substituting in equation d:

-3y - 9 (3.952) = 11

y = (11 + 9 (3.952) / - 3

= - 15.52.

Now find x by substituting for y an z in equation a:

x - 15.52 - 3.952 = 5

x = 5 + 15.52 + 3.952

= 24.476.