一、解方程。
$x + 2.65 = 3.24$ $(x + 12)\times6 = 108$ $2x + 0.4x = 48$
$x - 0.36x = 16$ $7.5x - 9.5\times4 = 8.5$ $54\div2 + 3x = 72$
$9.4x + 4.5x = 1.39$ $2\times0.9 + 0.3x = 7.8$ $2x - 18 = 2.8$
$0.7(x + 0.9) = 42$ $2x\times0.25 = 8$ $3.18\times2 + 2x = 14.26$
$4.2x + 18.6 = 31.2$ $4x - 18 = 0.24$ $3.1x\div2 = 1.24$

$x = 0.59$
$x = 6$
$x = 20$
$x = 25$
$x = 6.2$
$x = 15$
$x = 0.1$
$x = 20$
$x = 10.4$
$x = 59.1$
$x = 16$
$x = 3.95$
$x = 3$
$x = 4.56$
$x = 0.8$

二、计算下面各题，怎样简便就怎样计算。
$6.5\times1.78 + 1.78\times3.5$ $168.1\div(4.3\times2 - 0.4)$ $5.32 - 0.375 + 0.68 - 0.625$
$(0.125\times8 - 0.5)\times4$ $25.2\div(14.2 - 7.2 - 2.8)$ $[4.8 - (5.2 - 1.6)]\div0.16$
$9.85\div0.125 + 2.15\times8$ $47\times2.8 + 52\times2.8 + 2.8$ $33.02 - (148.4 - 90.85)\div2.5$
$0.52 + 3.64\div5.2\times9.6$ $19.2\times75 - 7.5\times92$ $19.55\div[(1.25 + 0.45)\times23]$
$0.25\times(4.8 - 7.5\div3)$ $0.02\div(2.1 - 2.09)\times1.5$ $[0.15 + (2.4 - 1.8)]\times20$

17.8 20.5 5
2 6 7.5
96 280 10
7.24 750 0.5
0.575 3 15