Is it better to cram the night before an exam or spend a little time each day studying?
Spend a little time each day studying.
Is -5 - -7 positive or negative?
It is positive. When you subtract a negative number, it is the same as adding the magnitude of the negatives number.
Are children born with the same number of bones as they will have as adults?
No, an infant has over 300 bones where as an adult has 206. This is because over development some bones fuse together.