d=c-11
Explanation:
d is desk
c is chair
The height of the d (desk) is always going to be 11 inches shorter than the chair. So subtract 11 from c (chair) and you will find d (desk).
If the chair is 13 inches....
d=13-11
d=2
If the chair is 32
d=32-11
d=21
This equation will work with numerous numbers to find the size of the desk. If you want you can find the height of the chair as well!