Page 20 - Counting Cars is Fun_名编辑电子杂志大师在线案例演示(www.mingbianji.com)
P. 20
Another car stps at the petol
staton – how many cars are there
now, can you count with me?
Now there are no cars driving on
the road!
One minus one
is zero!
-=
1-1=0
