解比例。
$5:2 = x:4$ $\frac{1}{3}:x = \frac{1}{4}:\frac{1}{5}$
$18:36 = 2:x$ $\frac{1}{3}:\frac{1}{2} = x:\frac{1}{4}$
$\frac{2}{8} = \frac{5}{x}$ $3x:\frac{1}{3} = 6:\frac{1}{6}$
$18:3 = x:3$ $4:x = 2:5$
$\frac{x}{15} = \frac{10}{75}$ $4:8 = x:10$
$\frac{5}{8} = \frac{25}{x}$ $7x:\frac{7}{5} = \frac{2}{3}:25\%$

解：$2x = 5×4$
$2x = 20$
$x = 10$
解：$\frac{1}{4}x = \frac{1}{3}×\frac{1}{5}$
$\frac{1}{4}x = \frac{1}{15}$
$x = \frac{4}{15}$
解：$18x = 36×2$
$18x = 72$
$x = 4$
解：$\frac{1}{2}x = \frac{1}{3}×\frac{1}{4}$
$\frac{1}{2}x = \frac{1}{12}$
$x = \frac{1}{6}$
解：$2x = 8×5$
$2x = 40$
$x = 20$
解：$3x×\frac{1}{6} = \frac{1}{3}×6$
$\frac{1}{2}x = 2$
$x = 4$
解：$3x = 18×3$
$3x = 54$
$x = 18$
解：$2x = 4×5$
$2x = 20$
$x = 10$
解：$75x = 15×10$
$75x = 150$
$x = 2$
解：$8x = 4×10$
$8x = 40$
$x = 5$
解：$5x = 8×25$
$5x = 200$
$x = 40$
解：$7x×25\% = \frac{7}{5}×\frac{2}{3}$
$\frac{7}{4}x = \frac{14}{15}$
$x = \frac{8}{15}$