# Chapter 4 - Elementary Number Theory and Methods of Proof - Exercise Set 4.4 - Page 189: 9

a. $5$ b. $3$

#### Work Step by Step

$$n=dq+r=d(n\ div\ d)+n\ mod\ d$$ $$28=5(28\ div\ 5)+28\ mod\ 5=5(5)+3$$ The numbers $n\ div\ d$ and $n\ mod\ d$ are defined to be the numbers $q$ and $r$, respectively, as given in the quotient-remainder theorem. See page 181 of the text.

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