Question

x : 5,4 = 10,2 : 1,8

Answer 1

$\frac{x}{5.4} = \frac{10.2}{1.8 } \\ x = \frac{10.2 \times 5.4}{1.8} = \frac{55.08}{1.8} = 30.6$

Answer 2

х:5,4=10,2:1,8
1,8х=10,2*5,4
1,8х=55,08
х=55,05:1,8
х=30,6
Проверка
30,6:5,4=10,2:1,8