Work backwards.
Start with z = 4.
Now deal with the middle equation
y + 3z = 11 Substitute z = 4 and solve for y
y + 3(4) = 11 Subtract 12 from both sides
y + 12 = 11
y + 12 - 12 = 11 -12 Combine terms on the left and right
y = - 1 Now use the top equation for x
z = 4 z still = 4
2x + 4(-1) +3(4) = 14
2x - 4 + 12 = 14 Solve 3z
2x + 8 = 14 Subtract 8
2x + 8 - 8 = 14 - 8 Combine
2x = 6 Divide by 2
x = 6/2
x = 3
Answer
x = 3
y = - 1
z = 4