Решить уравнение. 4,9: 0,35=х: 39; х/21=9/14; х/16=3/8; 108/90=42/b риешите подробнее

4,9:0,35=Х:39;
0.35x = 4.9 * 39
0.35x = 191.1
x = 191.1 / 0.35
x = 546

х/21=9/14;
14x = 9 * 21
14x = 189
x = 189/14
x = 13 1/2

х/16=3/8;
8x = 16 * 3
8x = 48
x = 48/8
x = 6

108/90=42/b
108b = 42 * 90
108b = 3780
b = 3780/108
b = 35