(1)5x-8.3=10.7,
5x-8.3+8.3=10.7+8.3,
5x=19,
5x÷5=19÷5,
x=3
4
5 ;
(2)3.6x-2.8x=12,
0.8x=12,
0.8x÷0.8=12÷0.8,
x=15.