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1300 - (b + 800) = 400

600*20 - n = 60

(600 - 500) : y = 20

d : (1300 - 800) = 4

1300 - (b + 800) = 400

1300 - b - 800 = 400

500 - b = 400

-b = - 100

b = 100

1300 - (100 + 800) = 1300 - 900 = 400

600*20 - n = 60

12000 - n = 60

-n = - 11940

n = 11940

600*20 - 11940 = 12000 - 11940 = 60

(600 - 500) : y = 20

100 : y = 20

y = 100 : 20

y = 5

(600 - 500) : 5 = 100 : 5 = 20

d : (1300 - 800) = 4

d : 500 = 4

d = 500*4

d = 2000

2000 : (1300 - 800) = 2000 : 500 = 4