Find the domain of the following piecewise function. f(x)= 2 if 2< x < 4 x+3 if 4< x< 8 2x if x=8 a) [2,8) b) (4,8] c) [4,8) d) (2,8] if you know the answer explain it, .

It is D (2,8]  because  it does not include 2  but includes 8.

Assuming that these two equations aren't being multiplied:

solve the second equation for y

5y+9z=1   5y=1-9z    y=(1-9z)/5

substitute y for 0

0=(1-9z)/5

5=1-9z
We could leave it like this, but I'm not going to because it feels so unfinished.
5-1=-9z
4=-9z
-4/9=z

x+z=6

x-(4/9)=6
x=6+(4/9)
x=58/9