5)ширина равна (80 : 5/16 -80*2) : 2 = 48cм
А) 6 2/25+7 23/25-4 1/40=13 25/25+4 1/40=14+4 1/40=18 1/40
б) 20 1/19- 4 12/19-5 17/19=381/19-88/19-112/19=181/19=9 10/19
в)(6 5/24+7 19/24)-6 19/23-5 9/23=13 24/24-1 10/23=14-1 10/23=
=13 23/23-1 10/23=12 13/23
<span>2х+3(х-3)=31,
2х+3х-9=31,
5х-9=31,
5х=31+9,
5х=40,
х=40:5,
х=8.
Ответ: 8.
</span><span>
(х+1)×3+4х=24,
3х+3+4х=24,
7х+3=24,
7х=24-3,
7х=21,
х=21:7,
х=3.
Ответ: 3.</span>