3-10х-20=7-2х
-10х+2х=7+17
-8х=24
Х=24:(-8)
Х=-3
<span> 5x</span>²<span> - x+4
б
5x</span>²-(x-4)
а
5x²+(4-x)
3x-6y=12
3x+5y=100
3x-6y=12
+
-3x-5y=-100
____________
-11y=-88
y=8
x=(12+6y)/3 = 3(4+2y)/3
x=4+2y
x=4+2*8=20
Ответ (20;8)
1)
а) 5/6-7/9=25-42/30=-17/30
б) 5 3/4 х 12 = 23/4 х 12 =23х3=69
6-15 и 2×6-5
-9 и 7........