i got a question like this:

Use the technique developed in this section to solve the minimization problem.
Minimize C=x-3y+z
subject to x-2y+3z<=30
2x+y-2z<=45
2x+y+3z<=40
x>=0, y>=0, z>=0

so i try to use simplex method to solve it, but...

1 -2 3 1 0 0 0 30
2 1 -2 0 1 0 0 45
2 1 3 0 0 1 0 60
-1 -3 -1 0 0 0 1 0

am i doing right to set up the initial simplex tableau?

i dont know what i should do with this: C=x-3y+z
also, what pivot element should i choose?
if the question like this:

2 1 3 1 0 0 45
4 1 5 0 1 0 45
-1 -2 -1 0 0 1 100


thank you so much