AB= √(-1+5)²+(6-3)²=√16+9=√25=5
BC=√(-5+2)²+(3+1)²=√9+16=√25=5
AC=√(-1+2)²+(6+1)²=√50=5√2
P=5+5+5√2=10+5√2
<span>9 4/31-(6 8/31+2 4/31)= 23/31
6 8/31 + 2 4/31 = 8 12/31
9 4/31 - 8 12/31 = 8 35/31 - 8 12/31 = 23/31
</span>
<span>10 1/25+ 9 24/25 - 6 9/25=. 13 16/25</span>
(12:3+4)*5=40
12:3=4
4+4=16
16*5=40
5(42,2х-3)=х+10
211х-15=х+10
210х=25
х=25/210=5/42