The total number of basketball is twice that of football. If the number of basketball sold every day is twice that of football, then basketball will be sold out with football.

Now we sell 20 footballs and 30 basketballs every day. After a few days, there were 120 basketballs left.

If we sell 20 footballs and 40 basketballs every day (twice as much as football), we will sell 40-30 more basketballs every day, and10 more in a few days.

So the actual number of days sold is

120 ÷ (30+10-30) =12 (days)

So the original football: 20x 12 = 240 (pieces)

A: There are 240 original soccer balls.