Question

Solve the system of equations 3y+2z=12 and y-z=9

Answer 1

Mulitply second equation by 2 and add to first

3y+2z=12
2y-2z=18 +
5y+0z=30

5y=30
divide 5
y=6

sub back
y-z=9
6-z=9
minus 6
-z=3
times -1
z=--3

x=-3
y=6