Ratio is a comparison of two values or two quantities.
Fraction is a another form of ratio.
The first term and the second term in the ratios are important.
It should not be changed.
The first quantity value is in first term and the second quantity value is in second term of the ratio.
Ratio and fractions are same.
Example:
The ratio of male to female in the school is 5 : 6.
5 represents male students and 6 represents female students.
The fraction form of the above ratio is 
Yes he does.
If the sales tax is 6%, that means that he has to pay an extra 6 cents for every dollar.
6x7.5=45
$7.50+$0.45=$7.95
9 x 0.55 = 4.95, which can be rounded to the ones place.
5 books remain.