Решение на фотографии
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X+y=36}
x-2=0.8(y+2)}
x=36-y
36-y-2=0.8(y+2)
36-2-y=0.8*y+0.8*2
34-y=0.8y+1.6
-y-0.8y=1.6-34
-1.8y=-32.4
y=-32.4/(-1.8)
y=18
x=36-18
x=18
Ответ: 18
-679+28-(45-679)=(открываем скобки) -679+28-45+679= 28-45=-17
8.75=10.5:x
8.75=105/10:x
8.75=105/10x
8.75=21/2x,x=o
17.5x=21
X=21:17.5
X=1.2