Answer: i needed this question too!
Let's call the width of our rectangle
and the length
. We can say
, since the length is equal to 4 cm greater than the width.
Also remember that the perimeter of a rectangle is the sum of two times the width and two times the length, or
. To solve this problem, we can substitute in the information we know, as shown below:




Now, we can substitute in the width we found into the formula for length, which is
:


The width of our rectangle is
cm and the length of our rectangle is 
True. it can only be written as one repeating number because eventually, a set of numbers would cancel out i think

has ten elements, so any proper subset has at most nine of these elements.
The number of ways of taking any

letters from this set is given by the binomial coefficient,

and in particular, the total number of ways to picking proper subsets is

Without computing each term directly, let's instead use a direct result from the binomial theorem, which says

If we replace

, then we're left with

We can use this to evaluate our sum directly: