1) {(у+х)/ху=7/ху |•ху
{(х–у)/ху=3/ху |•ху
{у+х=7
{х–у=3
{х=7–у
{7–у–у=3
–2у=–4
у=2
х=7–2=5
Ответ: (5;2)
2) {(n+m)/mn=5/mn |•mn
{(2m–n)/mn=1/mn |•mn
{n+m=5
{2m–n=1
{n=5–m
{2m–5+m=1
3m=6
m=2
n=5–2=3
Ответ: m=2; n=3
3) {(3y+x)/xy=13/xy |•xy
{(8y–2x)/xy=16/xy |•xy
{3y+x=13
{8y–2x=16
{x=13–3y
{8y–2(13–3y)=16
8y–26+6y=16
14y=42
y=3
x=13–3•3=13–9=4
Ответ: (4;3)