(1)2x+2.8×2=10.4
2x+5.6=10.4
2x+5.6-5.6=10.4-5.6
2x=4.8
2x÷2=4.8÷2
x=2.4
(2)5(3.2+x)=45.5
5(3.2+x)÷5=45.5÷5
3.2+x=9.1
3.2+x-3.2=9.1-3.2
x=5.9
(3)(x-5)÷4.5=6
(x-5)÷4.5×4.5=6×4.5
x-5=27
x-5+5=27+5
x=32
(4)x-0.35x=1.3
0.65x=1.3
0.65x÷0.65=1.3÷0.65
x=2