А)400+f:80=600
f:80 = 600-400
f:80 = 200
f = 200*80 = 1600
б) 500*x-600=400
500*x = 400 + 600
500*x = 1000
x = 2
в)1300-(b+800)=400
-(b+800)=400-1300
-b-800 = - 900
- b = - 900+ 800
- b = -100
b = 100
г) 600*20-n=60
600*20-n=60
12000-n = 60
12000- 60 = n
n = 11 940
д)(600-500):y=20
100:y=20
у = 5
е)d:(1300-800)=4
d : 500 = 4
d = 500*4
d = 2 000