Question 1150850
1)
Let,

the {{{CP}}} of the goods is {{{100x}}}

{{{M }}}gets profit of {{{15}}} %

{{{15}}} % of {{{CP}}}: {{{(15/100 )*100x }}}

selling price by{{{ M }}}:

{{{CP + profit=100x + 15x=115x}}}


cost price for {{{N}}} is now {{{115x}}}

{{{N}}} makes {{{5}}}% loss :

{{{(5/100)115x =575x/100=5.75x}}}


selling price by {{{N=cost_ price - loss=115x - 5.75x=109.25x }}}


but the selling price is given :

{{{13.11 = 109.25x}}}

{{{x = 13.11/109.25= 0.12 }}}


cost price of the goods :

{{{100x=100 * 0.12=12}}}

{{{M }}}paid {{{12}}} for buying the goods


2) 

{{{Profit}}}% = {{{(Profit/ Cost_ Price)*100}}}

{{{Profit = Selling_ Price - Cost_ Price}}}

let the cost price of the book be{{{ x}}}

{{{24}}}% ={{{0.24}}} of the cost price is {{{0.24x}}}

so, 

{{{x+0.24x=34.10}}}

{{{1.24x=34.10}}}

{{{x=34.10/1.24}}}

{{{x=27.5}}}

then a profit {{{28}}}% will be {{{0.28(27.5)=7.7}}} and  the selling price will be {{{27.5+7.7=35.2}}}