1. 解方程。
$5x + 3.25×4 = 17$ $\frac{2}{3}x + \frac{1}{2}x = 42$

解：
$5x + 3.25×4 = 17$
$5x + 13 = 17$
$5x = 17 - 13$
$5x = 4$
$x = 0.8$
解：
$\frac{2}{3}x + \frac{1}{2}x = 42$
$\frac{4}{6}x + \frac{3}{6}x = 42$
$\frac{7}{6}x = 42$
$x = 42 × \frac{6}{7}$
$x = 36$

2. 脱式计算。（能简算的要简算）
$3.6÷[(1.2 + 0.6)×5]$ $\frac{1}{15}×(\frac{1}{3} + \frac{1}{12})$
$\frac{7}{15}×(\frac{5}{7} - \frac{3}{14}÷\frac{3}{4})$ $\frac{3}{5}×\frac{1}{9} + \frac{2}{5}÷9$
$(70 + \frac{1}{68})×\frac{1}{69}$ $1 - 1÷2 - 1÷3 - \frac{1}{6}$

$231\frac{231}{232}÷231$ $8.89×36 + 8.89×63 + 8.89$
$2007×\frac{2005}{2006}$ $216×\frac{1}{3}×(\frac{1}{3} - \frac{1}{24})$

$3.6÷[(1.2 + 0.6)×5]$
$=3.6÷[1.8×5]$
$=3.6÷9$
$=0.4$
$\frac{1}{15}×(\frac{1}{3} + \frac{1}{12})$
$=\frac{1}{15}×(\frac{4}{12} + \frac{1}{12})$
$=\frac{1}{15}×\frac{5}{12}$
$=\frac{1}{36}$
$\frac{7}{15}×(\frac{5}{7} - \frac{3}{14}÷\frac{3}{4})$
$=\frac{7}{15}×(\frac{5}{7} - \frac{3}{14}×\frac{4}{3})$
$=\frac{7}{15}×(\frac{5}{7} - \frac{2}{7})$
$=\frac{7}{15}×\frac{3}{7}$
$=\frac{1}{5}$
$\frac{3}{5}×\frac{1}{9} + \frac{2}{5}÷9$
$=\frac{3}{5}×\frac{1}{9} + \frac{2}{5}×\frac{1}{9}$
$=(\frac{3}{5}+\frac{2}{5})×\frac{1}{9}$
$=1×\frac{1}{9}$
$=\frac{1}{9}$
$(70 + \frac{1}{68})×\frac{1}{69}$
$=(69 + \frac{69}{68})×\frac{1}{69}$
$=69×\frac{1}{69} + \frac{69}{68}×\frac{1}{69}$
$=1 + \frac{1}{68}$
$=1\frac{1}{68}$
$1 - 1÷2 - 1÷3 - \frac{1}{6}$
$=1 - \frac{1}{2} - \frac{1}{3} - \frac{1}{6}$
$=1 - (\frac{3}{6}+\frac{2}{6}+\frac{1}{6})$
$=1 - 1$
$=0$
$231\frac{231}{232}÷231$
$=(231 + \frac{231}{232})×\frac{1}{231}$
$=231×\frac{1}{231} + \frac{231}{232}×\frac{1}{231}$
$=1 + \frac{1}{232}$
$=1\frac{1}{232}$
$8.89×36 + 8.89×63 + 8.89$
$=8.89×(36+63+1)$
$=8.89×100$
$=889$
$2007×\frac{2005}{2006}$
$=(2006 + 1)×\frac{2005}{2006}$
$=2006×\frac{2005}{2006} + 1×\frac{2005}{2006}$
$=2005 + \frac{2005}{2006}$
$=2005\frac{2005}{2006}$
$216×\frac{1}{3}×(\frac{1}{3} - \frac{1}{24})$
$=72×(\frac{8}{24} - \frac{1}{24})$
$=72×\frac{7}{24}$
$=21$