You can
put this solution on YOUR website!I prefer elimination (maybe it's the cathartic suggestion of violence...)
adding -3 times the 1st to the 2nd ___ -7Y + 5Z = 35 ___ A
adding 5 times the 1st to the 3rd ___ 11Y - 8Z = -56 ___ B
adding 8 times A to 5 times B ___ -Y = 0 ___ Y = 0