Answer:
[tex]A=3.5\cdot{x}[/tex]
Step-by-step explanation:
Area is defined as width mutiplied by length. We assume the desk is rectangle. The following equation represents the area of the desk:
[tex]A=3.5\cdot{x}[/tex]
A is the area and x is the length. We can therefore determine the length:
[tex]x=A/3.5=42/3.5=12[/tex]
The length is 12 ft