tan4ik3107 (2 8/9х-2 1/4): 2 1/12=3/5
2 8/9х-2 1/4=3/5*2 1/12
2 8/9х-2 1/4=3/5*25/12
2 8/9х-2 1/4=5/4
2 8/9х=1 1/4+2 1/4
2 8/9х=3 2/4
х=14/4 : 2 8/9
х=14/4 : 26/9
х=14/4 * 9/26
х=7*9/4*13
х=63/52
х=1 11/52

Валентина409 (28,9х-21,4):21,12=3,5
(28,9х-21,4)=3,5*21,12
28,9х-21,4=73,92
28,9х=73,92+21,4
28,9х=95,32
х=95,32:28,9
х=3,29
(28,9*3,29-21,4):21,12=3,5
(95,08-21,4):21,12=3,5
73,68:21,12=3,5
3,49=3,5
3,5=3,5