There is no picture attached so not sure what you are talking about
15,75 - 100 %
100 % = 100/100 = 1
Then every number multiplied by 1 is 100 % of itself.
If the book was marked up 65% of what is was before, it makes a price of 165% when compared to the original.
165% = 165/ 100 = 1,65
15,75 . 1,65 = 25,9875
25,99 is the nearest option.
a)25,99

=47.8888 when you round it up you can get get about 48 then you estimate to about 50.
D=√(0.9²+2.5²)=2.65
The distance between two points is 2.65