3)
x+y=45
x/y=7/8
x=45-y
(45-y)/y=7/8
x=45-y
(45-y)*8=y*7
x=45-y
360-y*8=7*y
x=45-y
y=24
x=45-24=21
Ответ:x=21,y=24;
2)
x+y=31
x+2=9*(y-10)
y=31-x
x+2=9*(31-x-10)
y=31-x
x+2=9*(21-x)
y=31-x
x+2=189-9*x
y=31-x
x=18,7
y=31-18,7=12,3
Ответ:x=18,7;y=12,3
1)
x+y=25
x*8-y*5,5=92
x=25-y
(25-y)*8-y*5.5=92
x=25-y
13.5*y=108
x=25-y
y=108/13.5
x=25-y
y=8
x=25-8=17
Ответ:x=17,y=8;