решение смотрите на фотке....
(x-1 2/5):10+7 5/12=9
<span> <span> (x-1 2/5):10=9-7 5/12 </span></span>
<span><span> </span></span><span><span> <span>(x-1 2/5):10=8 12/12-7 5/12</span></span> </span><span> </span>
<span> <span> (x-1 2/5):10=1 7/12 </span></span>
<span><span> </span></span><span>x-1 2/5=19/12*10</span>
<span>x=190/12+7/5</span>
<span>x=95/6+7/5</span>
<span>x=475/30+42/30</span>
<span>x=517/30</span>
<span>x=17 7/30</span>
<span>
</span>
<span>
</span>
<span />
25<x<<span>60
</span>30, 36, 42, 48, 54.
1200-х+387=0
-х=-387-1200
-х=-1587
х=1587