Question

F(x,y,z)=66+5y+7+5t-9

Answer 1

1) X + Y = 10
2) X + Z = 20
3) Y + Z = 24
what is X + Y + Z = ?

From equation 1, x = 10-y
Plug 10-y in place of x in equation 2

10-y+z = 20 subtract 10 from both sides
-y + z = 10

We now have 2 equations with just y and z

-y + z = 10 new equation
y + z = 24 add the 2 equations
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2z = 34
z = 34/2
z = 17

We now have the value of z.
Plug that into equation 3

y + z = 24
y + 17 = 24
y = 24-17
y = 7

We now have the value of both z and y.
Plug the value for y into equation 1 to find x

x + y = 10
x + 7 = 10
x = 10-7
x = 3

Your values are x = 3, y = 7, z = 17