3,5х+х=9,9 9с-8,67с=0,6699 (10,49-а): 4,02=0,805 (y+26,1)×2,3=70,84 , 6 класс.

1) 3.5х+х=9.9
4.5х=9.9
х=9.9:4.5
х=2.2
2) 9с-8.67с=0.6699
0.33с=0.6699
с=0.6699÷0.33
с=2.03
3) (10.49-а):4.02=0.805
10.49-а=0.805×4.02
10.49-а=3.2361
а=3.2361-10.49
а=-7.2539
4) (у+26.1)×2.3=70.84
2.3у+60.03=70.84
2.3у=70.84-60.03
2.3у=10.81
у=10.81÷2.3
у=4.7