(х + 57) / 2,5 = (2х - 1) / 4
4(х + 57)=2,5(2х - 1)
4x+228=5x-2,5
5x-4x=228+2,5
x=230,5
<span>6 4/7 < х/7 < 7 3/7
</span><span>46/7 < х/7 < 52/7
</span>х = 47, 48, 49, 50, 51
...........................................................................................................................
1200 - 100\% 100\% -x =?
1020 - x
1200 * x = 1020 * 100
x = 1020 * 100 / 1200
x = 85
1) 100\% - 85\% = 15\%
ответ 15\%