Think about the mathematical process you use as you solve the following problems. Show your work and your solutions.  

1. If there are $100$ students in a room and $40$ of them are taller than $5$ feet, how many are not taller than $5$ feet?

   Hint (a):

   Since there are $40$ students taller than $5$ feet out of $100$ students, the rest of the students are not taller than $5$ feet. So subtract $40$ from $100$ to get the number of students that are not taller than $5$ feet.

   Answer (a):

   $100-40=60$ students are not taller than $5$ feet

2. If there are $17$ blue and white stripes on a flag and $9$ of them are blue, how many are white?

   Hint (b):

   See part (a).

3. If there are $250$ pennies and dimes in a box and $130$ of them are pennies, how many are dimes?

   Hint (c):

   See part (a).

4. Now it is time to generalize. Imagine you know how many items you have in a collection of two types of things. If you know how many of one of the items you have, how could you find how many of the other item you have?

   Hint (d):

   Describe the process used in part (a).