I take the bus to the libary after school and travel 3 miles, then my mom pics me up and we travel 4 miles home. how far do I live from my school

I'm pretty sure its 7. You drive 3 miles to school from the library. Its 4 miles home from the library. If you take the miles driven from library to school, and add the miles driven from library to home, it would be 7 miles from school to home.

This is most like a pythagorean triple triangle and the triple being 3-4-5, you would like 5 miles from the school.