(99 - 9х) * 8 + 14 = 86
(99 - 9х) * 8 = 86 - 14
(99 - 9х) * 8 = 72
99 - 9х = 72 : 8
99 - 9х = 9
9х = 99 - 9
9х = 90
х = 90 : 9
х = 10
--------------------------
Проверка: (99 - 9 * 10) * 8 + 14= 86
(99 - 90) * 8 + 14 = 86
9 * 8 + 14 = 86
72 + 14 = 86
86 = 86
/х/2,6 = 0,91
<span>1) 2,6х=0,91 </span>
<span>2)-2,6х=0,91 </span>
<span>1) х1=0,91 : 2,6 </span>
<span>х1=0,35 </span>
<span>2) х2=0,91 : (-2,6) </span>
<span>х2=-0,35 </span>
9+8+7+6+5+4+3+2+1=45 птиц
15+14+13+12+11+10+9+8+7+6+5+4+3+2+1=120 птиц
20+19+18+17+16+15+14+13+12+11+10+9+8+7+6+5+4+3+2+1=200 птиц