15 3/8÷(2 3/4 х + 5 5/6) -1 1/2 =3/4
(2 3/4 х + 5 5/6) -1 1/2 =123/4*4/3
2 3/4 х + 5 5/6 -1 1/2 =41
2 3/4 х =44+1 1/2-5 5/6
2 3/4x=42 1/2-5 5/6
2 3/4x=36 4/6
x=220/6*4/11
x=20/3*2=40/3=13 1/3
21 22 23 24 25 26 27 28 29 30
<span>21+29=50 </span>
<span>22+28=50 </span>
<span>23+27=50 </span>
<span>24+26=50 </span>
<span>50*4+25+30 = 200+55=255 </span>
<span>Все остальное - аналогично...</span>