1)(а-b)*2 = 2a-2b
<span>2)(а+b)^2 =36
2a+2b=36
2a=36-2b
a=18-b
3) </span><span>а^2 -b^2=24
2a-2b=24
2a=24+2b
a=12+b</span>
30 процентов. 90-100
27-x
x=30
2 вроде ....................................
1) 4 1/9:х=7,4
4 1/9=7,4*х
х=4 1/9:7,4
х=37/9 :37/5=37/9*5/37=5/9
х=5/9