Alright, the way to do this is to subtract one letter with each equation. For 3, we can multiply the first equation by 3 and add it on to the next to get -4x+5y=6 (we eliminated the z). Next, we can also eliminate the z in the third equation by multiplying the first one by -8 and adding on to that, getting -6x-12y=-14
After that, we have -4x+5y=6 and -6x-12y=-14. You can multiply the second equation by -2/3 and add on to get -3y=(-28/3)+6 and y=-((-28/3)+6)/3. Solve from there by plugging it in for variables as shown, then with z after x. The next two are similar, but feel free to ask if you have any issues with those!