一、解方程。
$0.3x + 1.1 = 3.8$
$2x - 1 = 4×0.6$
$4.2x + 6.2×3 = 31.2$
$5x + 3x = 12.8$
$6x = 0.64×12$
$x - 48 + 22 = 26.8$
$10.5 + 3x = 16.2$
$2.5x - 0.5÷0.2 = 7.5$
$7(x - 36) = 35.7$
$3x - 24 = 0.96$
$2(8x - 3x) = 12$
$(64 + 6x)÷2.8 = 40$
$0.52x - 0.12x = 16.8$
$6x÷3 = 1.98$
$2.7x + 3.3x - 11.4 = 6.6$

1. 解方程$0.3x + 1.1 = 3.8$
解：
$0.3x+1.1 = 3.8$
$0.3x=3.8 - 1.1$
$0.3x=2.7$
$x = 2.7÷0.3$
$x = 9$
2. 解方程$2x - 1 = 4×0.6$
解：
$2x-1 = 4×0.6$
$2x-1 = 2.4$
$2x=2.4 + 1$
$2x=3.4$
$x = 3.4÷2$
$x = 1.7$
3. 解方程$4.2x + 6.2×3 = 31.2$
解：
$4.2x+6.2×3 = 31.2$
$4.2x+18.6 = 31.2$
$4.2x=31.2 - 18.6$
$4.2x=12.6$
$x = 12.6÷4.2$
$x = 3$
4. 解方程$5x + 3x = 12.8$
解：
$5x+3x = 12.8$
$8x = 12.8$
$x = 12.8÷8$
$x = 1.6$
5. 解方程$6x = 0.64×12$
解：
$6x = 0.64×12$
$6x = 7.68$
$x = 7.68÷6$
$x = 1.28$
6. 解方程$x - 48 + 22 = 26.8$
解：
$x-48 + 22 = 26.8$
$x-(48 - 22)=26.8$
$x-26 = 26.8$
$x = 26.8+26$
$x = 52.8$
7. 解方程$10.5 + 3x = 16.2$
解：
$10.5+3x = 16.2$
$3x = 16.2 - 10.5$
$3x = 5.7$
$x = 5.7÷3$
$x = 1.9$
8. 解方程$2.5x - 0.5÷0.2 = 7.5$
解：
$2.5x-0.5÷0.2 = 7.5$
$2.5x - 2.5 = 7.5$
$2.5x = 7.5+2.5$
$2.5x = 10$
$x = 10÷2.5$
$x = 4$
9. 解方程$7(x - 36) = 35.7$
解：
$7(x - 36)=35.7$
$x - 36 = 35.7÷7$
$x - 36 = 5.1$
$x = 5.1+36$
$x = 41.1$
10. 解方程$3x - 24 = 0.96$
解：
$3x-24 = 0.96$
$3x = 0.96+24$
$3x = 24.96$
$x = 24.96÷3$
$x = 8.32$
11. 解方程$2(8x - 3x) = 12$
解：
$2(8x - 3x)=12$
$2×5x = 12$
$10x = 12$
$x = 12÷10$
$x = 1.2$
12. 解方程$(64 + 6x)÷2.8 = 40$
解：
$(64 + 6x)÷2.8 = 40$
$64 + 6x = 40×2.8$
$64 + 6x = 112$
$6x = 112 - 64$
$6x = 48$
$x = 48÷6$
$x = 8$
13. 解方程$0.52x - 0.12x = 16.8$
解：
$0.52x - 0.12x = 16.8$
$0.4x = 16.8$
$x = 16.8÷0.4$
$x = 42$
14. 解方程$6x÷3 = 1.98$
解：
$6x÷3 = 1.98$
$6x = 1.98×3$
$6x = 5.94$
$x = 5.94÷6$
$x = 0.99$
15. 解方程$2.7x + 3.3x - 11.4 = 6.6$
解：
$2.7x + 3.3x - 11.4 = 6.6$
$6x-11.4 = 6.6$
$6x = 6.6+11.4$
$6x = 18$
$x = 18÷6$
$x = 3$
综上，方程的解依次为：$x = 9$；$x = 1.7$；$x = 3$；$x = 1.6$；$x = 1.28$；$x = 52.8$；$x = 1.9$；$x = 4$；$x = 41.1$；$x = 8.32$；$x = 1.2$；$x = 8$；$x = 42$；$x = 0.99$；$x = 3$。