30*(60+а)=4500 120-40/k=40 (300-n)/20=9 70*x-150=60 5600/(360/k-20)=80

30*(60+а)=4500
60+a = 150
a = 150-60
a = 90

120-40/k=40
40/k = 120-40
40/k = 80
k = 80:40
k = 1/2

(300-n)/20=9
300-n = 180
n = 300-180
n = 120

70*x-150=60
70x = 60+150
70x = 210
x = 3

5600/(360/k-20)=80
360/k-20=5600/80
360/k-20 = 70
360/k = 70+20
360/k = 90
k = 360/90
k = 4