一、口算。
$1 - 86\% =$ $\frac{1}{4}×\frac{12}{7} =$ $3.75÷50\% =$
$3.2 - 0.32 =$ $\frac{2}{3}÷\frac{5}{6} =$ $\frac{8}{13} + \frac{18}{13} =$
$\frac{3}{4}÷3 =$ $3.14×0.6 =$ $\frac{1}{6} - \frac{1}{24} =$
$5^{3} =$ $\frac{5}{36}÷\frac{10}{9} =$ $28×12.5\% =$
$20.3 - 19.9 =$ $\frac{5}{8} + \frac{3}{5} =$ $235 + 598 =$
$0.78÷0.5 =$ $\frac{3}{4} - \frac{1}{10} =$ $\frac{2}{7}÷\frac{1}{2} =$
$\frac{3}{5} - \frac{1}{2} =$ $\frac{3}{8}×\frac{2}{9} =$ $12×\frac{5}{24} =$

一、0.14 $\dfrac{3}{7}$ 7.5 2.88 $\dfrac{4}{5}$ 2 $\dfrac{1}{4}$ 1.884 $\dfrac{1}{8}$ 125 $\dfrac{1}{8}$ 3.5 0.4 $\dfrac{49}{40}$ 833 1.56 $\dfrac{13}{20}$ $\dfrac{4}{7}$ $\dfrac{1}{10}$ $\dfrac{1}{12}$ $\dfrac{5}{2}$

$\frac{13}{20}$ $\frac{4}{7}$ $\frac{1}{12}$ $\frac{5}{2}$

二、解方程。
$4 - 3x = 2$ $x - 25\%x = 10.5$ $x + \frac{1}{4}x = \frac{2}{7}×\frac{5}{6}$
$5(x - 0.4) = 27.5$ $x÷(1 - 44\%) = 6.5$ $25\%x - 0.6 = 0.2x$

二、$x=\dfrac{2}{3}$ $x=14$ $x=\dfrac{4}{21}$ $x=5.9$ $x=3.64$ $x=12$