1)
{5p-3q=0 /x4
{3p+4q=29 /x3
{20p-12q=0
{9p+12q=87
{29p=87
p=3
9+4q=29
4q=20
q=5
2)
{4u+3v=14
{5u-3v=25
9u=39
u=39/9=13/3
52/3+3v=14
3v=14-52/3
3v=-10/3
v=-10\9
3)
{10p+7q=-2
{2p-22=5q
{10p+7q=-2
{2p-5q=22 /x(-5)
{10p+7q=-2
{-10p+25q=-110
32q=-112
q=-112/32=-7/2
10p-49/2=-2
10p=-2+49/2
10p=45/2
p=45/20=9/4
4)
{2u+5v=0 /x4
{-8u+15v=7
{8u+20=0
{-8u+15v=7
35v=7
v=7/35=1/5
2u+1=0
2u=-1
u=-1/2