Question

x+y=8 x+z=12 x+t=16 x+u=20 y+z+t+u=44

Answer 1

adunam primele 4 relatii

(x+y)+(x+z)+(x+t)+(x+u)=8+12+16+20
4x+y+z+t+u=56

de aici scadem a 5-a relatie

4x+y+z+t+u-(y+z+t+u)=56-44
4x=12
x=12:4
x=3

3+y=8; y=8-3; y=5
3+z=12; z=12-3; z=9
3+t=16; t=16-3; t=13
3+u=20; u=20-3; u=17