‼️PLEASE HELP I HAVE NO IDEA ON HOW TO DO THIS‼️‼️

Solve each system by elimination. Please show the work.

1. 3x+3y+6z=9; 2x+y+3z=7; x+2y-z=-10

2. 3x-y+z=3; x+y+2z=4; x+2y+z=4

3. x-2y+3z=12; 2x-y-2z=5; 2x+2y-z=4