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