Write expressions to represent the quantities described below.  

1. If Thompson Valley High School has $x$ students and if Erwin Middle School has $342$ fewer students, how many students does Erwin Middle School have?

   Answer (a):

   $x-342$

2. If $w$ represents the width of a rectangle and if its length is twice its width, how long is the rectangle?

   Hint (b):

   Follow the steps in part (a).

   Answer (b):

   $\text{length}=2w$

3. When Mr. Van Exel bought his laptop, he paid $\$400$ more than three times the amount he paid for his camera. If he paid c dollars for his camera, then how much did he pay for his laptop?

   Hint (c):

   Identify the important information in the word problem.

   Hint 2(c):

   Follow the steps in part (a).

   Answer (c):

   cost of the laptop $=3(c)+400$