11/13 = х/10,4;
13х = 11*10,4;
х = 11*10,4/13;
х = 8,8
2/7 = х/12,6
7х = 2*12,6;
х = 2*12,6/7;
х = 3,6
х/4,5=3/7,5;
7,5х = 4,5*3;
х = 4,5*3/7,5;
х = 1,8
1) 320 - 20 = 300
2) 300 + 180 = 480
3) 120 : 3 = 40
4) 120 + 180 = 300
5) 700 - 100 = 600
6) 210 * 2 = 420
7) 60 * 3 = 180 минут.