1) 
x-y=6
x=6+y 6+у+6у+у^2=-4
у^2+7у+10=0
у1= -2
у2= 5
х1= 6+2= 8
х2= 6-5 = 1
ответ: (8; -2) ; (1;5)
5) 
у-х+3=0
-х=-3-у
х= 3-у 3-у-1=y^2
-у^2-у+2=0
y^2+y-2=0
y1= 1
y2= -2
x1= 3-1 = 2
x2= 3+2 = 5
ответ: (2;1) ; (5;-2)
3) 
x-y=1
-y=1-x
y= x-1 x^2-2x+2-26=0
x^2-2x-24=0
x1= 6
x2= -4
y1= 6-1 = 5
y2= -4-1 = -1
ответ: (6;5) ; (-4; -1)
№ 1. 5 : (64 - х) = 230
64 - х = 5 : 230
64 - х = 5/230 = 1/46
х = 64 - 1/46
х = 63 45/46
Проверка: 5 : (64 - 63 45/46) = 230
5 : 1/46 = 5 * 46/1 = 230 - верно.
№ 2. х : 4 - 95 = 125
х : 4 = 125 + 95 = 220
х = 220 * 4
х = 880
Проверка: 880 : 4 - 95 = 220 - 95 = 125 - верно.
№ 3. 21995 + 4062 - (192 - 220) * 7 : 623 * 21 - 25 =
1) 192 - 220 = - 28; 2) -28 * 7 = -196; 3) -196/623
4) - 196/623 * 21 = - 4116/623 = - 6 378/623 = - 6 54/89
5) 21995 + 4062 = 26057; 6) 26057 - (-6 54/89) = 26063 54/89
7) 26063 54/89 - 25 = 26038 54/89
ответ 45