Basic calculator problem

i tried a lot of times to solve this challenge but i am not able yo solve this challenge ,
please help me in any way , if we have received any

of the character out of * + _ / %
then we can store this in character , but how to use this character for further calculation,

suppose i receive ch as (+ )
i store this ch value , now i want to do addition of two no,s NI and N2 now how is it poosible to get the value which is received in ch ,

if i write

cout<<N1<<ch<<N2 then this line gives me output as N1 +N2 , not the solution,

this is the main problem where i stuck,

in short i dont know how to use this ch value for solving expressions