答案：$6800÷400$
$=(\underline{100}×68)÷(\underline{100}×4)$
$=\underline{68}÷\underline{4}$
$=\underline{17}$
$0.26÷0.02$
$=(\underline{0.01}×26)÷(\underline{0.01}×2)$
$=\underline{26}÷\underline{2}$
$=\underline{13}$
$\frac{3}{7}÷\frac{5}{14}$
$=\frac{(\ 6\ )}{14}÷\frac{5}{14}$
$=(\underline{6}×\underline{\frac{1}{14}})÷(\underline{\frac{1}{14}}×5)$
$=\underline{6}÷\underline{5}$
$=\underline{\frac{6}{5}}$

答案：$84÷6$
$=84×\frac{1}{6}$
$=14$
$0.84÷0.06$
$=0.84×\frac{100}{6}$
$=14$
$\frac{14}{27}÷7$
$=\frac{14}{27}×\frac{1}{7}$
$=\frac{2}{27}$
$\frac{14}{27}÷\frac{7}{9}$
$=\frac{14}{27}×\frac{9}{7}$
$=\frac{2}{3}$

答案：设 $0.84÷4=a$,则
$0.84=a×4$
$0.84×\frac{1}{4}=a×4×(\frac{1}{4})$
$0.84×\frac{1}{4}=(a)$
又因为 $0.84÷4=a$,所以 $0.84÷4=0.84×(\frac{1}{4})$