Question

if x-y + z = 19 , y + z =20 , x-z=3 , find d value of x+4y-5z

Answer 1

If x-y + z = 19 , y + z =20, x-z=3,

solving these, we get 
x=15,y=8, z=12

x+4y -5z= 15+32-60 = -13 .. none of these.

Answer 2

Answer:

Value of x+4y - 5z is  - 13

Step-by-step explanation:

x- y + z = 19    ,,,,,,(1)

y +z = 20      ,,,,,,,,,, (2)

Adding eq. (1) and (2) we get

x- y+z +y+z =19 +20

x +2z = 39   ,,,,,,,,,(3)

x- z =3    ,,,,,,,,(4)

Subtracting eq. 4 from 3

x+ 2z - (x - z) = 39 - 3

   3z = 36

 z = 36 / 3=12

Putting the value of z in eq.2

  y + 12 =20

   y = 20 -12=8

Putting the value of y and z in eq.1

x - 8 + 12 = 19

  x +4 = 19

  x= 19 - 4 =15

Value of x +4y - 5z

                          = 15 + 4 × 8 -5 ×12

                          = 15 +32- 60

                        = 47 - 60 =- 13