You'd better change the way____you speak to your parents.为什么

the way后面的定语从句,关系词若在从句中作状语,相当于“用这种方式 / 方法(=in this way)”时,通常不用关系词,偶尔用that,在较正式的文体里才用in which来引导.如：
Do it the way （that）you were taught.要照教你的那样做
I was impressed by the way in which she did it.
她干成这件事的方式给我留下了深刻的印象.
这种用法如果省略掉the way,就可以改用how引导的从句.
I was impressed by the way in which she did it.=I was impressed by how she did it.