For shopkeeper A, Let the number of red pens sold be ‘x’. Then, the number of blue pens sold = 55% of x = 0.55x Now according to question, => x + 0.55x = 310 => x = 200 Number of red pens sold = 200 Number of blue pens sold = 0.55x = 110 Number of black pens sold = 110 × (9/11) = 90 Similarly, we can find the required data for the other shopkeeper too. Required sum = 90 + 75 = 165