12:x=4.5 5.8 = 15;y 8:3=16:2 2,4:x=0,8:5 Z: 4,2=9:10,8 X/7,8 = 1/0,3 0,7/y = 2,1/33

Решим пропорции:

1. $$12:x = 4:5$$
   $$x = \frac{12 \cdot 5}{4} = \frac{60}{4} = 15$$
2. $$5.8 = 15y$$
   $$y = \frac{5.8}{15} = \frac{58}{150} = \frac{29}{75} \approx 0.3867$$
3. $$8:3 = 16:z$$
   $$z = \frac{3 \cdot 16}{8} = \frac{48}{8} = 6$$
4. $$2.4:x = 0.8:5$$
   $$x = \frac{2.4 \cdot 5}{0.8} = \frac{12}{0.8} = 15$$
5. $$z:4.2 = 9:10.8$$
   $$z = \frac{4.2 \cdot 9}{10.8} = \frac{37.8}{10.8} = 3.5$$
6. $$\frac{x}{7.8} = \frac{1}{0.3}$$
   $$x = \frac{7.8}{0.3} = 26$$
7. $$\frac{0.7}{y} = \frac{2.1}{33}$$
   $$y = \frac{0.7 \cdot 33}{2.1} = \frac{23.1}{2.1} = 11$$

0,8:y=2:1/4 x/4=0,5/0,3 48/5,1=y/3,4 12/0,5=30/2 0,4/7=z/4,2

1. $$0.8:y = 2:\frac{1}{4}$$
   $$y = \frac{0.8 \cdot \frac{1}{4}}{2} = \frac{0.8}{8} = 0.1$$
2. $$\frac{x}{4} = \frac{0.5}{0.3}$$
   $$x = \frac{4 \cdot 0.5}{0.3} = \frac{2}{0.3} = \frac{20}{3} \approx 6.6667$$
3. $$\frac{48}{5.1} = \frac{y}{3.4}$$
   $$y = \frac{48 \cdot 3.4}{5.1} = \frac{163.2}{5.1} = 32$$
4. $$\frac{12}{0.5} = \frac{30}{2}$$
   $$24 = 15$$

   Это не пропорция, a равенство неверно

5. $$\frac{0.4}{7} = \frac{z}{4.2}$$
   $$z = \frac{0.4 \cdot 4.2}{7} = \frac{1.68}{7} = 0.24$$

Ответ: Решения уравнений выше