-x-4 +5x+15=-5-5x-2
-x+5x+5x=-5-2+4-15
9x=-18
x=-2
<span>(1)а*b=b*a.<span>(2)a*(b+c)=(a+b)*c.<span>(3) (a*b)*c =(a*c)*b.<span>(4)a(b-c)=a*b-a*c.</span></span></span></span>