Write an algebraic expression for each situation.  

1. Three less than a number.

   Hint (a):

   See problem 3-39 for examples of how to write these expressions.

2. Nine more than three times a number.

   Hint (b):

   If $9$ more than a number is $n+9$, then what is $9$ more than three times a number?

   Answer (b):

   $3n+9$

3. Two less than five times a number

   Hint (c):

   See part (b).