Question 1062294
x, original quantity of sunglasses
x-10, how many actually shopkeeper did sell
p, original price for 1 sunglasses pair
{{{300/x=p}}}, original price, again


Revenue:  {{{(p+4)(x-10)}}}
Cost:  300
PROFIT:  {{{(p+4)(x-10)-300=100}}}


Make the substitution for original price because that is based on the original x sunglass pairs.


{{{highlight((300/x+4)(x-10)-300=100)}}}


The easier part is now to just solve this equation.