a+4/a-a+6/a+2=4/a+6/a+2=(4+6)/a+2=10/a+2
1)(8a³-b³)/(4a²-b²)=(2a-b)(4a²+2ab+b²)/(2a+b)(2a-b)=(4a²+2ab+b²)/(2a+b)
2)(ab+ac)/(ab-3b+ac-3c)=a(b+c)/(b(a-3)+c(a-3))=
=a(b+c)/(a-3)(b+c)=a/(a-3)
___________
21y = 63
y = 3
5 * 3 - x = 8
15 - x = 8
x = 7
Ответ : ( 7 ; 3)