Hi! This is my first post and hopefully someone will be able to help me! I have tried this problem atleast 10 times but I am just getting frustrated... it's not working! Here it is:

you have to solve for x, y, and z.. and I could get one but then it doesnt work for the other problems...

2x+y+z=4

3x-y+4z=11

x-y+5z=20