9x=31,8-3,9
9x=27,9
x=3,1
2100-100%
1575-x
2100x=1575*100
x=75%
100%-75%=25%
Ответ:25%
1) 23/10
2) 6/1000 = 3/500
3) 540/100 = 27/5
4) 9/1