1. 解方程或比例。
$x:\frac{1}{2}=\frac{2}{3}:4$ $\frac{x}{4}=\frac{6}{5}$

第一题：
解：$4x = \frac{1}{2} × \frac{2}{3}$
$4x = \frac{1}{3}$
$x = \frac{1}{3} ÷ 4$
$x = \frac{1}{12}$
第二题：
解：$5x = 4 × 6$
$5x = 24$
$x = \frac{24}{5}$

2. 脱式计算。（能简算的要简算）
$24×(\frac{1}{4}+\frac{5}{6}-\frac{7}{8})$ $0.25×4.7+\frac{1}{4}×5.3$
$12500÷12.5×8$ $(\frac{2}{9}+\frac{4}{21}×\frac{7}{8})÷\frac{11}{18}$
$[3.2×(1-\frac{5}{8})+3\frac{3}{5}]×2\frac{1}{12}$ $\frac{43}{97}×98$
$1\frac{3}{7}+2\frac{4}{15}+4\frac{4}{7}+3\frac{2}{15}$ $\frac{1}{4}×\frac{2}{5}÷(\frac{3}{4}+\frac{3}{8})$
$1÷2.5+2.5×0.4$ $3.75×4\frac{2}{5}+1.6×3\frac{3}{4}$

$24×(\frac{1}{4}+\frac{5}{6}-\frac{7}{8})$
$=24×\frac{1}{4}+24×\frac{5}{6}-24×\frac{7}{8}$
$=6+20-21$
$=5$
$0.25×4.7+\frac{1}{4}×5.3$
$=0.25×4.7+0.25×5.3$
$=0.25×(4.7+5.3)$
$=0.25×10$
$=2.5$
$12500÷12.5×8$
$=1000×8$
$=8000$
$(\frac{2}{9}+\frac{4}{21}×\frac{7}{8})÷\frac{11}{18}$
$=(\frac{2}{9}+\frac{1}{6})÷\frac{11}{18}$
$=(\frac{4}{18}+\frac{3}{18})×\frac{18}{11}$
$=\frac{7}{18}×\frac{18}{11}$
$=\frac{7}{11}$
$[3.2×(1-\frac{5}{8})+3\frac{3}{5}]×2\frac{1}{12}$
$=[3.2×\frac{3}{8}+3.6]×\frac{25}{12}$
$=[1.2+3.6]×\frac{25}{12}$
$=4.8×\frac{25}{12}$
$=10$
$\frac{43}{97}×98$
$=\frac{43}{97}×(97+1)$
$=\frac{43}{97}×97+\frac{43}{97}×1$
$=43+\frac{43}{97}$
$=43\frac{43}{97}$
$1\frac{3}{7}+2\frac{4}{15}+4\frac{4}{7}+3\frac{2}{15}$
$=(1\frac{3}{7}+4\frac{4}{7})+(2\frac{4}{15}+3\frac{2}{15})$
$=6+5\frac{6}{15}$
$=6+5\frac{2}{5}$
$=11\frac{2}{5}$
$\frac{1}{4}×\frac{2}{5}÷(\frac{3}{4}+\frac{3}{8})$
$=\frac{1}{10}÷(\frac{6}{8}+\frac{3}{8})$
$=\frac{1}{10}÷\frac{9}{8}$
$=\frac{1}{10}×\frac{8}{9}$
$=\frac{4}{45}$
$1÷2.5+2.5×0.4$
$=0.4+1$
$=1.4$
$3.75×4\frac{2}{5}+1.6×3\frac{3}{4}$
$=3.75×4.4+1.6×3.75$
$=3.75×(4.4+1.6)$
$=3.75×6$
$=22.5$