Răspuns:
a)-×+y=7
×=5-3y
-(5-3y)+y=7
y=3
×=5-3×3
×=-4
(-×,y)=(-4,3)
-(-4)+3=7
-4+3×3=5
7=7
5=5
b)×+y=4
×=14+y
14+y+y=4
y=-5
x=14-5
x=9
c)3×+y=13
y=7-×
3×+7-×=13
×=3
y=7-3=4
d)3y=7-5×
-×-3y=1
-×-(7-5×)=1
-2-3y=1
×=2
y=-1