7 1/8 = 7*8 + 1 = 57/8
3 4/5 = 5*3 + 4 = 19/5
Исходное не пишу
9а+15-7а-11=0
2а=-4
а=-2
5х+у=7
7х-4у=-1
...
20х+4у=28
7х-4у=-1
...
27х=27
х=1
у=2
---------------
5х-2у=16
8х+3у=38
...
15х-6у=48
16х+6у=76
...
31х=124
х=4
у=2
--------------
4а+6b=9
3a-5b=2
...
-12a-18b=-27
12a-20b=8
-38b=-19
b=0,5
a=-0,1
<span>9х-6х=24
3х=24
х=24/3
х=8
<span>2х+4х=24
6х=24
х=24/6
х=4
</span></span>
213-2x=927:9
213-2x=103
2x=213-103
2x=110
x=110:2
x=55