Насчет рисунка не уверена!!
Как-то так/
X*16:8=80
x=x*8=80
x=10
Проверим:
10*16:8=80
<span><span><span><span>
а
</span><span>
10
</span><span>
100
</span><span>
1000
</span><span>
10000
</span><span>
100000
</span></span><span><span>
а*10
</span><span>
100
</span><span>
1000
</span><span>
10000
</span><span>
100000
</span><span>
1000000
</span></span><span><span>
а:10
</span><span><span> 1</span></span><span>
10
</span><span>
100
</span><span>
1000
</span><span>
10000
</span></span><span><span>
а+10
</span><span>
20
</span><span>
110
</span><span>
1010
</span><span>
10010
</span><span>
100010
</span></span><span><span>
а-10
</span><span>
0
</span><span>
90
</span><span>
990
</span><span>
9990
</span><span>
99990
</span></span></span></span>
С=2πr=2•3.14•4=25.12
S=πr В квадрате=3.14•4в КВ.=3.14•16=50,24
Ответ: 50,24;25,12