21 = 3*7
28 = 2*2*7
<span> НОК(21, 28) = 2*2*3*7 = 84</span>
(9+8)х=136
17х=136
х=136:17
х=8
38х-25х+18=200
13х+18=200
13х=200-18
13х=182
х=182:13
х=14
×=504-186
×=318
318+186=504
ответ:×=318
1) 2Ι-1,8Ι - Ι-1,2Ι = 3,6 - 1,2 = 2,4
2) 2Ι 1 3/8Ι - Ι - 7/8Ι = 2 Ι 11/8Ι - Ι - 7/8Ι = 11/4 - 7/8 = 22/8 - 7/8 = 15/8 = 1 7/8