原式=12.6乘(100-1)=12.6乘100-12.6乘1=1260-12.6=1247.4
12.6×99=1260-12.6=1247.4
12.6×99=12.6×100-12.6×1=1260-12.6=1247.4
12.6x(100-1)=12.6x100-12.6x1=1260-12.6=1247.4
=12.6x(100-1)=12.6x100-12.6x1=1260-12.6=1247.4