(0.5(x+y)/3z+0.5(x+y)/z=20
умножим обе части на 3z
0.5(x+y) +3*0.5(x+y)=3z*20
вынесем за скобки x+y :
(x+y) (0.5+1.5)=60z
(x+y) *2 = 60z
x+y = 30z
y=60z-x
(0.5(x+y)/3z+0.5(x+y)/z=20
0.5(x+y) +3*0.5(x+y)=3z*20
0.5x+0.5y+3*0.5*(x+y)-3z*20=0
0.5x+0.5y+1.5*(x+y)-3z*20=0
0.5x+0.5y+1.5x+1.5y-3z*20=0
2x+0.5y+1.5y-3z*20=0
2x+2y-3z*20=0
2x+2y-60z=0
x+y=30z
y=30z-x
