#### Answer

a. $4$
b. $7$

#### Work Step by Step

$$n=dq+r=d(n\ div\ d)+n\ mod\ d$$
$$43=9(43\ div\ 9)+43\ mod\ 9=9(4)+7$$
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 pf the text.