A recursive definition for the sequence shown above can be x = n-5.
21 - 5 = 16
16 - 5 = 11
11 - 5 = 6
and so on...
The number sequence has a difference of 5 in each of the values before and after them.
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36 divided by 3 = 12
3 goes into 36 twelve times.
X - the number of pencils
y - the number of pens
She has twice as many pencils as she has pens.
Tom borrows a pen, so she has y-1 pens. Now she has ten less pens than pencils.
Set 2y and y+9 equal to each other:
She has 9 pens.