Решите уравнения:
(1600+t):80=60 
2000:f-670=1330
1300-(d-678)=400

(1600+t):80=60 1600+t=60*801600+t=4800t=4800-1600t=3200--------------(1600+3200):80=6060=602000:f-670=13302000:f=1330+6702000:f=2000f=2000/2000f=1------------------------2000:1-670=13301330=13301300-(d-678)=400d-678=1300-400d-678=900d=900+678d=1578--------------------------1300-(1578-678)=400400=400