3y-2x=69=> 1.5y-x=34.5
4.5x+2y=536=> x+(2/4.5)y=536/4.5
1.5y-x+x+(2/4.5)y=34.5+536/4.5
(27/18)y + (8/18)y = (621+2144)/18
(35/18)y=2765/18
y= 2765/35
y=79
3*79-2x=69
x=(237-69)/2
x=84
(a² -25) /(2a² +10a) =(a -5)(a +5) /2a(a +5) =(a -5) /2a,
при а =0
1) (a^2-5a+6)/(a^2+7a+12)*(a^2+3a)/(a^2-4a+4)=((a-3)(a-2))/((a+3)(a+4))*(a(a+3))/((a-2)(a-2))=(a(a-3))/((a-2)(a+4))
2) (x^2+2x-3)/(x^2+3x-10)*(x^2-9x+14)/(x^2+7x+12)=((x-1)(x+3))/((x-2)(x+5))*((x-7)(x-2))/((x+3)(x+4))=(x-1)(x-7)/(x+5)(x+4)
Вроде так, но могу ошибаться)