一、解方程。
x÷12 = 1.2
2x÷2.2 = 4.5
2x + 6x = 4.8
x + 4x - 11 = 2.9
7(x - 1.2) = 2.1
6x - 4.8×0.4 = 5.28
2(x + 1.7) = 9.2
8x - 4x = 0.64
1.2×0.2x = 0.12
6.2x - x = 416
7 + 2.5 + x = 13.8
(3.8 - 2)x = 14.4
0.2x + 3.2 = 4.7
12.5x - 10x = 4
8x÷7.2 = 0.6

$x = 14.4$
$x = 4.95$
$x = 0.6$
$x = 2.78$
$x = 1.5$
$x = 1.2$
$x = 2.9$
$x = 0.16$
$x = 0.5$
$x = 80$
$x = 4.3$
$x = 8$
$x = 7.5$
$x = 1.6$
$x = 0.54$

二、计算下面各题，怎样简便就怎样计算。
5.25×2 + 1.68
(6.7 - 1.69÷1.3)×400
0.63 + 0.84 + 0.37 + 8.16
6.66 + 3.63÷0.6 + 19.34
(6.02 + 2.8)÷4 - 2.05
0.84÷[(2.3 + 0.5)×0.6]
2.86×0.25 + 2.86×0.75
10.5×0.8 - 1.5×0.8
7.25 - (32.4 - 11.6)÷6.4
3.5÷0.7 + 0.5×1.7
(7.2×2.4 - 9.48)÷0.25
3.4×87 + 3.4×15 - 3.4×2
91.2÷24×(3.6÷0.9)
95÷[(1 + 0.9)÷0.1]
12.75 - 4.62 - 3.38 + 7.25

12.18 2160 10
32.05 0.155 0.5
2.86 7.2 4
5.85 31.2 340
15.2 5 12