6300: 90*с=350 , (3400-600): х=400 , 780-у=1440: 60 , а-15*30=320 , х-270=1150+630 , 150*20-а=1200

1. 70×c=350
C=350:70=5
2. 2800:x=400
X=2800:400=7
3. 780-y=24
y=780-24=756
4. a-450=320
a=450+320=770
5. x-270=1780
x=270+1780
x=2050
6. 3000-a=1200
a=3000-1200=1800