Multiply the second equation by -3 in order to cancel out U
3u+z=15
-3(u+2z)=10
3u+z=15
-3u-6z=-30. Then u subtract those two equations
-5z=-15
Z=3
To solve for u, plug in the z in one of the equation (doesn’t matter which one)
3u+3=15
3u=12
U=4
Ur answer is
U=4. Z=3
