I have a squared rectangle where I want to find the side length of a sub-square (for the record, consult the omniscient Google).
Here's what I've already done.
$$14 + 4 + x = \mathrm{height}.$$ The teeny square has a side length of 1. If the square to the right of the tiny square has side length $a$, $$x = 9 + a - 1.$$ This problem would be a lot easier if the rectangle were a square (if you think it is, prove it), but I'm not sure what to do now.