一、解方程。
3x - 0.2x = 16.8
8x÷25 = 16
32×4 + 8x = 250
1.5 + x = 6.26
5x - 7.2×3 = 3.4
(1.2 + 1.8)x + 6 = 168
5x + 34 = 54
x÷5 - 27 = 13
1.3x + 7.2x = 10.2
x - 0.5x = 14
0.5×50 + 0.5x = 35
x÷(2.1 + 4) = 8.5
5x + 3x = 20.8
6.8x - 68 = 6.8
2.8x - 2.5x = 7.5

$x = 6$
$x = 50$
$x = 15.25$
$x = 4.76$
$x = 5$
$x = 54$
$x = 4$
$x = 200$
$x = 1.2$
$x = 28$
$x = 20$
$x = 51.85$
$x = 2.6$
$x = 11$
$x = 25$

二、计算下面各题，怎样简便就怎样计算。
7.2×0.4 + 0.78
4.8 - 3.6×0.5 + 0.4
6.7 - 0.33×6.7 - 6.7×0.57
(3.96 - 1.98)×0.25
(6.02 + 2.8)÷0.4 - 2.05
7.5 + (32.4 - 11.6)÷0.64
2.86×0.35 + 2.86×0.65
2.8×5.6÷0.16 - 47
0.25×[(2.8 + 4.4)÷1.2]
6.8×87 + 6.8×14 - 6.8
5.8×12 + 7.8÷0.03
(71.2 - 71.2×0.9)÷0.25
9.12÷2.4×(3.6÷0.9)
19.5÷[(1 - 0.5)÷0.1]
[20 - (11.2 + 4.54)]÷0.6

3.66 3.4 0.67
0.495 20 40
2.86 51 1.5
680 329.6 28.48
15.2 3.9 7.1