1. 脱式计算。（能简算的要简算）
$(\frac{7}{9} + \frac{5}{6} - \frac{1}{4})×72$ $2.5×32×1.25$ $\frac{18}{23}÷\frac{8}{5} + \frac{18}{23}×\frac{3}{8}$
$5\frac{5}{8} - (3\frac{5}{8} + 1\frac{5}{7})$ $(\frac{2}{31} + \frac{3}{34})×31×34$ $(3.4 - 10\frac{4}{5}×\frac{2}{9})÷1\frac{3}{5}$

$\frac{8}{17}×80\% + \frac{9}{17}×0.8$ $18\frac{5}{7} - (8\frac{5}{7} - 1\frac{3}{4})$
$146×3.4 + 15.4×34$ $800 - 345÷1.5 + 263$

$(\frac{7}{9} + \frac{5}{6} - \frac{1}{4})×72$
=$\frac{7}{9}×72 + \frac{5}{6}×72 - \frac{1}{4}×72$
=56 + 60 - 18
=98
$2.5×32×1.25$
=$2.5×(4×8)×1.25$
=$(2.5×4)×(8×1.25)$
=10×10
=100
$\frac{18}{23}÷\frac{8}{5} + \frac{18}{23}×\frac{3}{8}$
=$\frac{18}{23}×\frac{5}{8} + \frac{18}{23}×\frac{3}{8}$
=$\frac{18}{23}×(\frac{5}{8}+\frac{3}{8})$
=$\frac{18}{23}×1$
=$\frac{18}{23}$
$5\frac{5}{8} - (3\frac{5}{8} + 1\frac{5}{7})$
=$5\frac{5}{8} - 3\frac{5}{8} - 1\frac{5}{7}$
=2 - $1\frac{5}{7}$
=$\frac{2}{7}$
$(\frac{2}{31} + \frac{3}{34})×31×34$
=$\frac{2}{31}×31×34 + \frac{3}{34}×31×34$
=2×34 + 3×31
=68 + 93
=161
$(3.4 - 10\frac{4}{5}×\frac{2}{9})÷1\frac{3}{5}$
=$(3.4 - \frac{54}{5}×\frac{2}{9})÷\frac{8}{5}$
=$(3.4 - 2.4)×\frac{5}{8}$
=1×$\frac{5}{8}$
=$\frac{5}{8}$
$\frac{8}{17}×80\% + \frac{9}{17}×0.8$
=$\frac{8}{17}×0.8 + \frac{9}{17}×0.8$
=0.8×($\frac{8}{17}+\frac{9}{17}$)
=0.8×1
=0.8
$18\frac{5}{7} - (8\frac{5}{7} - 1\frac{3}{4})$
=$18\frac{5}{7} - 8\frac{5}{7} + 1\frac{3}{4}$
=10 + $1\frac{3}{4}$
=$11\frac{3}{4}$
$146×3.4 + 15.4×34$
=$146×3.4 + 154×3.4$
=3.4×(146+154)
=3.4×300
=1020
$800 - 345÷1.5 + 263$
=800 - 230 + 263
=570 + 263
=833

2. 解方程。
$6x÷7 = 12$ $\frac{23}{4} = \frac{x}{8}$

解：$6x÷7 = 12$
$6x = 12×7$
$6x = 84$
$x = 84÷6$
$x = 14$
解：$\frac{23}{4} = \frac{x}{8}$
$4x = 23×8$
$4x = 184$
$x = 184÷4$
$x = 46$