1.
(х+7)/3 - (у-8)/5=3
(х+5)/4 +(у+9)/3=5
5(х+7) - 3(у-8)=3*3*5
3(х+5)+4(у+9)=5*4*3
5х+35 - 3у+24=45
3х+15+4у+36=60
5х - 3у= - 14 ( *4)
3х+4у=9 ( *3)
20х - 12у= - 56
9х+12у=27
29х=-29
3х+4у=9
х= - 1
-3+4у=9
х= -1
4у=12
х= -1
у=3
(-1; 3)
4.
(х-9)/3 - (у+10)/2=0
(х-7)/4+(у+10)/8= -1,5
2(х-9) - 3(у+10)=0
2(х-7)+у+10= - 1,5*8
2х - 18 - 3у- 30=0
2х - 14+у+10= - 12
2х-3у=48
2х+у= -8 ( *-1)
2х -3у=48
-2х - у=8
-4у=56
2х+у= -8
у= - 14
2х - 14= - 8
у= - 14
2х=6
у= -14
х=3
(3; -14)