why don't we

我们为什么不打网球呢？

___Why ___don't ___we play tennis?

我们为什么不找老师帮忙呢？

___Why ___don't ___we ask the teacher for help?

这个周末我们为什么不骑车去湖边呢？

___Why ___don't ___we ride bikes to the lake this weekend?