(1)5x+2.4×15=66 5x+36=66, 5x+36-36=66-36, 5x× 1 5 =30× 1 5 , x=6;(2)3.2x+2.8x-x=1, 5x=1, 5x× 1 5 =1× 1 5 , x= 1 5 .