I think on average a well-trained dog maybe knows like 15 commands or something.我认为任何一条训练有素的狗狗都能够学会至少15种指令什么的

on average:平均

We fail one student per year on average.

我们平均每年有一个学生不及格。

On average we receive five letters each day.

我们平均每天收到五封信。

But she is really able to learn this easily而她却轻而易举地学会了

be able to:会； 能

At this rate we won't be able to afford a holiday.

照这样下去，我们不会有时间／钱去度假的。

I may be able to help you in some way.

我也许可以从某个方面去帮助你。

近义词:

be capable of会

be in a position to能够