一、直接写出得数。
$1787 - 998 =$ $\frac{5}{8} + 0.25 =$ $\frac{10}{21}×\frac{3}{5} =$ $21÷\frac{3}{7} =$
$\frac{5}{9}×\frac{1}{5}÷\frac{5}{9}×\frac{1}{5} =$ $\frac{1}{8}÷\frac{1}{8}÷\frac{1}{8} =$ $\frac{1}{11}×12.1 - 1 =$
$\frac{3}{5} + \frac{2}{5}÷\frac{1}{5} =$ $6.3÷0.1 =$ $\frac{5}{6}÷\frac{6}{7} =$
$\frac{7}{9} - (\frac{5}{7} - \frac{2}{9}) =$ $8×(2.5 + 0.25) =$ $3.37 + 6.73 =$
$\frac{5}{6} - \frac{1}{9} =$ $(0.18 + 0.9)÷9 =$ $7×\frac{1}{6}÷7×\frac{1}{6} =$

789；$\frac{7}{8}$；$\frac{2}{7}$；49；$\frac{1}{25}$；8；0.1；$\frac{13}{5}$；63；$\frac{35}{36}$；$\frac{2}{7}$；22；10.1；$\frac{13}{18}$；0.12；$\frac{1}{36}$

二、怎样简便就怎样算。
$2.5×1.25÷\frac{1}{32}$ $15×202.3 - 20.23÷\frac{1}{100} + 2023×50\%$
$(\frac{1}{2} + \frac{2}{3} + \frac{3}{4})×36$ $2023×\frac{123}{2024}$

答题卡作答：
$2.5×1.25÷\frac{1}{32}$
$=2.5×1.25×32$
$=2.5×4×(1.25×8)$
$=10×10$
$=100$
$15×202.3 - 20.23÷\frac{1}{100}+2023×50\%$
$=15×202.3 - 20.23×100+2023×0.5$
$=15×202.3 - 202.3×10+202.3×5$
$=202.3×(15 - 10 + 5)$
$=202.3×10$
$=2023$
$(\frac{1}{2}+\frac{2}{3}+\frac{3}{4})×36$
$=\frac{1}{2}×36+\frac{2}{3}×36+\frac{3}{4}×36$
$=18 + 24+27$
$=69$
$2023×\frac{123}{2024}$
$=(2024 - 1)×\frac{123}{2024}$
$=2024×\frac{123}{2024}-\frac{123}{2024}$
$=123-\frac{123}{2024}$
$=122\frac{1901}{2024}$

三、解方程。
$\frac{1}{4}x + \frac{6}{7}x = 3.1$ $\frac{1}{4}x - 6 = \frac{1}{5}x + 14$
$4:3x = 4:9$ $\frac{1}{4}x + 50\%x = \frac{3}{4}$

三、解方程。
1. $\frac{1}{4}x + \frac{6}{7}x = 3.1$
解：$(\frac{7}{28} + \frac{24}{28})x = 3.1$
$\frac{31}{28}x = \frac{31}{10}$
$x = \frac{31}{10} ÷ \frac{31}{28}$
$x = \frac{28}{10} = 2.8$
2. $\frac{1}{4}x - 6 = \frac{1}{5}x + 14$
解：$\frac{1}{4}x - \frac{1}{5}x = 14 + 6$
$\frac{5}{20}x - \frac{4}{20}x = 20$
$\frac{1}{20}x = 20$
$x = 20 × 20 = 400$
3. $4:3x = 4:9$
解：$4 × 9 = 4 × 3x$
$36 = 12x$
$x = 36 ÷ 12 = 3$
4. $\frac{1}{4}x + 50\%x = \frac{3}{4}$
解：$\frac{1}{4}x + \frac{1}{2}x = \frac{3}{4}$
$\frac{1}{4}x + \frac{2}{4}x = \frac{3}{4}$
$\frac{3}{4}x = \frac{3}{4}$
$x = 1$