how far is it from your school to your home 里from your schoo

from your school to your home 做实际主语
it做形式主语,由于真正的主语from your school to your home太长,放在句子开头会显得头重脚轻,故用it做形式主语代替from your school to your home,而把真正的主语放在句子后面.
how far is it from your school to your home＝from your school to your home is how far.