<span>60*(с*3)=189720</span>
<span>60*3с=189720</span>
<span>3с=189720:60</span>
<span>3с=3162</span>
<span>с=3162:3</span>
<span>с=1054</span>
(а-в)-(а-в)=а-в-а+в=0(с-д)-(с+д)=с-д-с-д=-2д(u+v)-(v-u)=u+v-v+u=2um-(n-p-m)=m-n+p+m=2m-n+p(a+b)-(b+c)- (a-c)=a+b-b-c-a+c=0(k+m)+(m-k)+(m-k)=k+m+m-k+m-k=3m-k<span>(b+1)-(a-1)-(b-a)=b+1-a+1-b+a=2</span>