С×6=360
7×a=490
360:a=60
490: a=70
X:6=60
C:7=70

с*6=360;
c=360:6;
c=60.

7*a=490;
a=490:7;
a=70.

360:a=60;
a=360:60;
a=6

490:a=70;
a=490:70;
a=7

x:6=60;
x=60*6;
x=360.

c:7=70;
c=70*7;
c=490.